My phone number is 456-123-XXXX (American phone number + area code). Over the past few months I get fairly regular spam calls from other numbers also beginning with 456-123-XXXX, where the last four digits are always different. The calls are clearly spam, telling me I won a trip and then asking for my credit card number. After getting one such call, I ignored it and called the number back. The guy that answered seemed genuinely confused and said he hadn't called me. I warned him that his number was likely being used for spam. I've already called my carrier, but the operator who answered seemed totally confused and basically just suggested I change my number, which I really don't want to do. My number is attached to a cell phone, although when I originally got it 15 years ago it was a landline.
So... what do I do? Also, I'm curious as to what's actually happening... as well as if my number is also being used to spam other people.