Wells Fargo Wells Fargo Student Loans Bill for erroneous loan Internet

I keep receiving a bill from Wells Fargo student loans. I have called them on several occasions and I have been told that the loan was purchased from another bank; however, I receive bills and statements from that company regarding the same loan. I asked Wells Fargo to show me in writing the proof that they now own the loan.  I was then put on hold then hung up on. I'm not really sure what to do, but I know I'm not paying them money for a loan I never got from them, especially when Im paying it to the other company.