vodacom - ruining my life

this has been the worst experience of my life thus far, it was a complete hassle that took almost a few weeks to cancel my contract with vodacom last year, i finally got in writing that my contract was cancelled last year, but now that im trying to apply for a house it says my account is in a arrears and this could ruin my chances at a new home. no one on the customer "Care" lines can help and when i try to phone the billing department it says that the number i had a contract with is invalid. im running in circles with vodacom