Funny, here it's domestic numbers that start in 44 that usually come with a potential spam warning. From what I can tell 44 is not an area code per se, it's a prefix for Voice over Internet Protocol (VoIP) phones. I am guessing call centers must use that type of phone.
On a forum for expats living here, a guy just reported yet another scam. We have a password called a clave única here. You use your equivalent of your Social Security Number and the clave única to enter many different government websites. It can be used to pay taxes, access government benefits, obtain important documents, etc. Anyways, he was trying to set up internet service with a new provider and the company asked for his clave única. Obviously, that's not something you want to give out to anyone. Fortunately, he asked the forum if this sounded fishy. The consensus was that it wold be a terrible idea to provide that.