Billing issues with Cell C

Cell C has the worst Billing system ever when i signed up for my contract i opted for a debit order because I didn't want issues of my phone line being cut well Cell C has decided to ignore my debit order and they have not debited my account as per my instruction and my agreement and now they have cut my services and they are now pinning all their billing issues on me i fail to understand how is it my fault that they didn't debit my account in the bank account supp**** on the date given to them how is this now my problem when this was working well before and they had a system issue now I must suffer for the past 3 months I have been back and forth trying to sort out this issues and I'm now exhausted I'm tired worst part I use my phone for work and they have cut off my line I'm so frustrated I don't know what to do now. I REGRET SIGNING UP WITH CELL C WORST SERVICE EVER.