Cellc still debits accounts after 24 month contract has ended.

Some years ago I had a 24 month contract with cellc that was paid up, only to find out today that they have continued debiting my acc after the “24 months”. I found this out from my credit report which is showing I am in arrears with cell c. This is such a ******* and from reading the comments I see that I’m not the only 1 that this has been done to! Please I need someone to contact me and I need a letter saying that this account has been paid up!