Debit order error

For past 7 months was jst problem after problem. First it was the deduction date. Now iTs the acc details used. I changed banking details on 29 may 2015 and yet end of june and july they still tried deducting from old bank account. Causing additional bank charges and bad mark against my cheque account. With this error they still want to charge me R70 for unpaid debit order. I must pay for their mistake. Now they also keep suspending my account for an amount i disputed so many times and every time have to hear we will provide feedback in 48 hours and no one calls. But they quick to block my line. I had enough of Cell C and their incompetence.