You say this number is version wireless but I do not have them as a cell carrier and never have. They do not leave a message and hang up when I do answer.
If this is a collection agency, even for Verizon or otherwise, it is illegal for them to call but not leave identification (I've worked with collections for over 20 years, and have been in charge of legal compliance for over half of them). If they are calling you after you've paid, that is also illegal, and most likely caused by a third party collector hired by the company. - If you talk to them, I'd notify them that they need to update there records, and I'd report them for bad collection practices. - If it's stating that it's several different things from collections to free trips, it's a scam, and anyone that confirms this (by talking to them), should report this as well. Both issues have federal government offices that work on this and you can report them to. A quick google search should work. I've never talked to them. I don't answer calls with numbers I don't know and are out of my area code, and if they don't leave a message they are not only breaking the law, but don't want to reach me too badly.