This number does appear to be generated from the USA, but it isn't, it's another way of getting around the system.
These are debt management chases.
Get prepared and get yourself a referees whistle, one good blast and they won't bother you again  

I've had 4 calls in the last 1 and a half hours!!!!  Is there any other way to get round them by calling them back and annoying them!!

Nigerian

I got almost 10 calls from this number

received 5 calls from this number I don't know