Contract cancellation

my contract ended in 1 April 2015.I gave them a notice in march that i`m cancelling the contract spoke to Tshepiso and received ref number ***.Last month they decided to bill my account with R206..00 and again this month of R206.00 . I called again just to find out that my call was never referred to the cancellation department .I Spoke to Tshepiso again of which he promised that the contract is cancelled ,The cancellation department called me to inform me that the contract is indeed cancelled. This month i received a bill again of which they deducted R206.00 again from my bank account ,clearly someone is not doing their job and of which i the consumer has to pay the price every day..I`m really not happy with this service i`m receiving from them .