Must pay for contract that i dont have

I have received numerous calls form autopage stating that I have to pay for a contract that I don't have with them. According to Autopage they can see that the cell phone has never been used. I have asked for a copy of the contract that they say I have signed. In this last six months I have received no assistance from Autopage. Every time I also have to pay a different amount. I have become so desperate that I paid an amount to just get this matter sorted because this is affecting my credit record. How can they expect me to pay for a phone that I never received and never used and that I don't have any documentation for.