Its a recorded message saying that it is not a valid number when it called less than two minutes prior to the return call. Most of these scams use a router or a dba wireless phone similar to basic phone, or any cell company like att also it functions like a landline. Also voip and skype is used through a laptop are used. This is not the first scam call ive gotten im quite sick of them. They pretend to be lawyer collection agencies and medical bill payment collection agencies. Something needs to be done because some people fall prey to this. Its call fraud it is a very serious offense.