Thieving Cell-C

It has been more than 2 months since l notified Cell-C that l did not want to renew my data contract with them once it has expired at the end of July. After a few calls to make sure that my number had been converted to prepaid, l was satisfied that l would pay my last bill at the end of August. However, Cell-C has just billed me AGAIN even though my contract ended, and l requested that l do not continue using their service. THIS IS THEFT! I want my money back!!!