Cancelation and pay back my money

Very bad I went to the store last year after my phone got ****** and asked them to cancel my contract and tell me the settlement amount. OK I went and back to the show them I have paid in full they said it's OK. After some time I took another contract and handset got ****** and I was told I have two contracts that was new to me and again the deducted more than what I need to pay for the month. What I do not understand is why would I pay telkom money knowing that I don't owe them.