Unauthorized Debit Order

Cell C has debited my account *******ly. I dont have a contract with them and this morning I find a debit order off my account for R112.80

What is going on. My bank cannot assist with reversing thia unauthorised debit of my bank account, so why is the network provider doing this.

FNB :-) Paid from a/c, 24 Mar: R112 Ref.Cell C Sp ***; Avail

Regards Chris