BAD CELL C ACCOUNTS SERVICE

I have been fighting with CELL C for 6 months regarding my debit order. They have my banking details correct as my 2nd contract goes off every month without a hitch. Every month the debit order does not go off from the 1st contract and then 3 days later they msg ME saying that I am overdue and havent paid. This is getting to a point where I am going to cancel my contracts when they expire end of this year.