Sorry to heard about your situation. My husband & I have been in a similar one and very recently too.
My mother-in-law (a real test to our marriage) & her now estranged husband had taken out several loans and never paid them back. The creditors were all over them and eventually us, her other kids and even ex-husband. The way they got our info was because they had used us as references on some of the misc. loans they had taken out (without asking!)
At first I was annoyed by the calls but then started to get a little leery and began checking our credit. Luckily we were safe but… she had dabbled in one the brothers credit. Borrowing in the wrong hands can be a bit of a downward spiral. I did give them the info I had (which they already had) and told them we really didn’t have any contact with them and the creditor never called again.
Rather than being mad at the callers, as they are just doing their jobs, maybe you should chat with your dad and see what the deal is. If the bills paid… they won’t call you anymore. If they are calling you this debt has gone unpaid for a very long time and if they have your info… perhaps he’s used your name as a reference at some point? Not trying to tick anyone off. I know how horrible it is to try and correct credit mistakes and problems and be annoyed by these people…but, why hasn’t anyone said hey … maybe this loan should be taken care of??? and no I’m not a creditor but I do work at a business that bills people and I know how ridiculous it is to try and get people to pay bad debts. Rather than being helpful they go on the defence, instead of being responsible and solving or at least attempting to solve the problem.
Good luck to you. You might want to get a credit report just for kicks and make sure your info is safe.
Also I know that there is a way to block certain phone numbers on your phone. Another good one is to ask them the name of the business (otherwise *69 them and google the number to get name) and tell them you are going to seek legal action of they keep harassing you.