Which mobile prefixes get the most spam reports in Spain

If you get a call from a number starting with 6 or 7, it isn't necessarily an ordinary person. Those ranges belong to Spanish mobile telephony, and that is precisely why scammers use them so much: they look like any old mobile. Here we explain which mobile prefixes attract the most reports, why it happens and how to react.

Unlike premium-rate prefixes (803, 806, 807, 905) or international ones, which we cover in other guides because their danger lies in the cost of the call, here we are talking about something else. The 6xx and 7xx mobiles don't charge you extra for picking up. The problem is trust: they were born so your family could call you, and today they are fraud's favourite disguise.

How do mobile prefixes work in Spain?

In Spain, every mobile number has nine digits and starts with 6 or 7. That's it. The 6xx range is the classic one, the one we've been using for decades. The 7xx range opened up later, when the 6 numbers started running out, so today both coexist with no technical difference for you as a user.

This is important to understand: a number starting with 7 is no more suspicious than one starting with 6. Both are legitimate mobiles. The idea that "the 7 numbers are all spam" goes around a lot, but it's a myth. What happens is that, being newer, many 7xx numbers were assigned in bulk to virtual operators (MVNOs) and to automatic dialling services, and that is where some campaigns concentrate. But 6xx carries fraud just the same. The leading digit tells you almost nothing on its own.

What does matter are the first three digits, what we call the prefix. Each numbering block (for example, 600, 622, 744, 711) is assigned to a specific operator through the CNMC. When a scammer "rents" or exploits numbering from an operator with little oversight, that specific prefix begins to rack up reports. In our operator directory you can see which prefixes belong to each company and how many blocked numbers each one carries.

Why does a legitimate mobile prefix end up full of spam?

Here's the key that almost nobody explains. A mobile prefix isn't "good" or "bad" from birth. It gets contaminated by how it's used. There are several mechanisms:

• Mass dialling from call centres. Many telemarketing and fraud campaigns use VoIP platforms that acquire blocks of mobile numbering so their calls look personal. If a company dials thousands of numbers a day from a handful of lines, those lines fill up with reports very quickly.
• Low-oversight numbering. Some virtual operators resell lines with little verification of who uses them. That attracts those who want to burn through numbers and discard them.
• Line recycling. A number is cancelled and, after a while, reassigned. If an abusive campaign used it before, the next holder inherits the bad reputation.
• Spoofing. And this is the final trap: many calls that seem to come from a 6xx or 7xx don't actually originate from that number. The caller ID is faked. We explain it in depth in our guide on how caller ID is spoofed.

That's why a "legitimate" mobile prefix can show up again and again in the reports: it isn't that the operator is complicit, it's that their numbering is the raw material of the deception.

What do community reports say about mobile prefixes?

At NoCall we collect reports from real people who flag a number as spam, scam, harassment, telemarketing or debt collection. We don't publish rankings of specific individual numbers (that could unfairly single out a person), but we do work with the overall picture by category and by operator.

What we see qualitatively is consistent: the bulk of reports of nuisance or fraudulent calls come from 6xx and 7xx mobile numbering, not from 9xx landlines. It makes sense. The 9xx landline "smells" of a company or a switchboard, and many people simply don't pick up. The mobile generates trust, feels close, and that's why it's the preferred channel for both aggressive telemarketing and fraud.

So you can see how Spanish numbering is distributed and what to expect from each type, this table works as a map:

Notice one thing: the danger of 6xx/7xx isn't the cost, it's the impersonation of trust. The danger of 803/806 is indeed the cost. They are two distinct threats and it's best not to mix them up.

Is it true that "neighbour spoofing" uses your own prefix?

Yes, and it's one of the most effective techniques. Neighbour spoofing consists of faking the caller ID so the call shows a number very similar to yours: the same first three or four digits. If your mobile is 6 12 34 56 78, they call you from a 6 12 34 XX XX. The brain reads it as "this is local, maybe I know this person" and you pick up.

It's pure psychological design. It doesn't mean your operator has been compromised or that someone from your area is calling you. It means the attacker has chosen to display a number with your same prefix to raise the odds that you'll answer. The defence is the same as always: the number you see on screen is not proof of identity. We develop this in the guide on how to read the risk signals of a number.

How can you tell if a mobile calling you is spam?

Don't rely on the prefix alone. A 6xx could be your neighbour or it could be a fraud campaign. What really works is combining several signals. Follow these steps when an unknown mobile rings:

1. Don't pick up on impulse. If you're not expecting the call, let it ring. Anyone with something legitimate to tell you will leave a message or try again.
2. Look up the number before calling back. Paste it into the NoCall directory and see whether other people have already reported it and why.
3. Pay attention to the pattern, not just the digits. Calls at odd hours, a few seconds of silence when you pick up (that gives away an automatic dialler), or hanging up on the first ring (wangiri) are red flags.
4. Be wary of urgency. If the voice rushes you, threatens to cut off a service or asks for details "to verify", stop. No bank or government body works that way over the phone.
5. Verify through a channel you choose. If they claim to be your bank, the tax office or a company, hang up and call the official number yourself, the one shown on their website or on the back of your card. Never the number that called you.

That last rule is the golden one and applies to any prefix. Whether the fraud arrives disguised as a bank or as the tax office, the approach is identical: hang up and verify on your own. We spell it out for specific cases in how to verify whether a call or text from your bank is real and in how to verify a notice from the tax office or Social Security.

What do I do if a specific prefix won't stop calling me?

If the same number or a block of prefixes is harassing you, you have room to act beyond just hanging up:

• Block it on your phone. On iPhone and Android you can ban numbers one by one or silence unknown callers. You'll find the details by operating system and by manufacturer in how to block spam calls on iPhone and in blocking spam calls on Android by manufacturer.
• Report it on NoCall. Every report helps the next person who gets that call see the warning. That's how a "clean" prefix gets flagged before it does more harm.
• If you run a business, blocking on the switchboard works differently. We cover it in blocking numbers on a landline and SME switchboard.

Be clear about one thing: blocking a number doesn't stop a campaign that recycles lines or uses spoofing. It gets that specific line off your back, but tomorrow they can call you from a different 6xx. That's why blocking is necessary but not sufficient. The real defence is not to automate your trust in what you see on screen.

Why are mobiles fraud's preferred channel?

It's worth understanding the attacker's logic, because it helps you stay one step ahead. A scammer wants three things: for you to pick up, for you to trust, and for you to find them hard to trace. The 6xx/7xx mobile gives them all three.

• Picking up. A mobile looks personal. Many people who ignore a 9xx will answer a 6xx.
• Trust. With neighbour spoofing, the number mimics yours. With brand impersonation, the caller ID can even show your bank's name.
• Hard to trace. Lines are burned through and discarded. By the time a prefix racks up reports, the campaign has already jumped to another block.

On that foundation they build the scripts you already know from other guides: the AI-cloned voice that mimics a relative, ping calls and OTPs via flash call, or the industrial operation of a fraudulent call centre from the inside. The mobile prefix is just the wrapping; the deception comes in what they tell you afterwards.

And there's one group especially exposed: older people, who tend to trust a voice on the phone more and not to check the number. If you care for someone like that, the guide on how to protect older people from phone scams will be useful to you.

Where can I look up prefixes and trends?

If you want to go beyond a one-off call and understand the full map, you have several tools:

• The prefixes section explains what each range of Spanish numbering means, landline and mobile.
• In trends you can see how phone spam is moving across the country, with aggregated community data.
• The list of operators tells you which company is behind each block of prefixes and how many blocked numbers it has accumulated.
• And in our guides you have the full set on how to identify, block and report.

For the broader context of the phenomenon, two companion reads: the data-driven X-ray of phone spam in Spain and the Q2 2026 phone threat report.

In summary

The mobile prefix that shows up on your screen tells you less than you think. 6xx and 7xx are legitimate ranges, with no real difference between them, and that is precisely why they are fraud's favourite disguise: they look like an ordinary person. The danger doesn't lie in the cost of the call, as with 803/806, but in the trust they generate. The rule that never fails: the number doesn't prove who is calling. Don't pick up on impulse, look up the number before returning a call, and always verify through a channel you choose yourself.

If you've received a suspicious call from a 6xx or 7xx mobile, report it in the NoCall directory. Every report helps the next person see the warning before picking up. You can also check the methodology we use to classify numbers and read more on the blog.