money on account not allocated correctly and taking more on instalments!!

I have been with Cell C for the past 10 years, some times good service and most of the time when its a really big problem, no service. For some reason my debit order did not go off last month, on seeing that i immediately phoned Cell c and asked where can i pay the money in and what should i use for reference seeing this is one amount. Well i did what i was told, on following up is was told to phone legal department, did that, got the sms saying your allocations is done?? Then i started getting phone calls, your account is in arrears, I explained, nobody knows how to allocate the money. The end of this month, some where taken twice, i am in arrears and my amounts are higher than the previous month???REALLY!!! CAN I GET A JOB AT CELL C, I will teach how to do allocations, i know the company is very big, but still?? Taking money from my bank account that does not belong to you??!! Please someone help me, i dont know how to communicate with Cell C???