Vodacom *****ing money

I opened a contract for my 3 children in March of 2016 for 3 iPhone 5s's. In February of this year I cancelled all 3 contracts. However, they kept billing me for the 3 devices and each month they kept saying this was the last month. March and April they at least still sent the airtime. In April I once again called the cancellation department and got 3 cancellation reference numbers to safeguard myself. However, on the first of May the debit order went off once again and the airtime wasnt even sent to any of the contracts. When phoning the customer care line they said if they reverse the debit order my account will be in arrears. Im now completely fed up with vodacom. I have 3 other contracts with them seperate from the 3 I've cancelled and if this is not resolved today I'm cancelling all debit orders going forward.