My dad has a Yahoo account and he received a phone call saying there had been complaint...

My dad has a Yahoo account and he received a phone call saying there had been complaints on this account for usage to foreign countries, this has definitely not happened. He continually receives harassing phone calls claiming to be from Yahoo but since he has been hacked before and his computer compromised he is leery of all this. He has had extensive clean up work done to his computer and is certainly not going allow anyone else access to that computer. The question here is, is this actually a Yahoo person calling in an effort to correct the problem or is it in fact another scam. The email address is Billy Dingler @yahoo. com. If you could please give verification of this* preferably to him,and if not to me it would be greatly appreciated. If it is in fact an issue, also a way to resolve it.*Thanks for any help.**Terry Dingler