Why cant CELLC assist their clients Poor Service

Cell C has become the worst network. I am so irritated. I change my banking details so that i can be sure i will have the funds available. so it was changed from one bank to another from the 25th to the 1st or 7th of each month. I made my payment 26th July and they debiting again. So i call in to find out *** coz i made a payment and now its a R710 that has been debited again. I call in in the CALL Centre cant help coz i failed at some Question . Yes PEOPLE OF CELL C i changed my banking details and i cant remember to what date but everything is right to my old banking details . You PEOPLE CAN EASILY TAKE MONEY BUT CAN ASSIST YOUR CLIENTS . SO i must go to a branch which Will cost me money . Why have a SERVICE CENTER when you as CellC Cant help.

I Want my account sorted I am irate and feel as CEllC has been taking me for a ride .