Telkom handed me over the debt collectors

hi, hope all is well, a debt collection agency is phoning me too say that I owe u almost R6000,00 saying that I am on a 2 year contract with telkom, I signed for a month too month contract, Telkom suspended my line a year ago , and I have never received an invoice or anything since then , please send me proof that I am on a 2 year contract and were I signed for this