Account Settlement

I had a contract with Vodacom and had two numbers/lines. when things were not going well at work I struggled with monthly payments, until both my numbers were suspended. I then made an arrangement to pay by debit order in order to settle the account. when I was finally retrenched, I went to Vodacom offices to pay the outstanding balance in full. I paid the amount that I was told was outstanding, and was told that the debit order would be cancelled automatically if I do not owe anything anymore, indeed no further debit order went through my bank account. I turned down their offer to re-activate my account as my number was already recycled. now I am harassed by BURNARD RAAFF & ASSOC who say my outstanding Vodacom account was handed over to them. now where does that come from if Vodacom went as far as cancelling the debit order arrangement when I settled my outstanding balance? why wasn't I informed by Vodacom if I still owed anything when I came to settle the balance? I am now unemployed and have no income, all of a sudden I owe R28,264.28 for what? I should not be blacklisted for your mistakes, and I should not be perpetually owing money even after coming forward to settle.