On airttv decoder deal a headache

I have a explora deal with on airtv which we clenched telephonically. I gave out my banking details for them to debit my account monthly. That was part of the deal. They once did not debit and when they phone I asked them what their problem is because there are sufficient funds in the account. They said that will not happen again. But now for 2 months they have not debited and I whatsapped and emailed them and nothing is forthcoming. Now transmission is closed, I paid multichoice but because the decoder is theirs, I cannot enjoy my benefits as I think they delinked their decoder from transmitting channels to our set. Please help me.