Cancellation of contract

My contract was due to expire end of March 2016, on 17th of January I went to N1 city to cancel my contract, they fax through the application of cancellation and printed me the transmission. In April I received another billing statement, when I phoned customer care they advise me my contract was not cancel i need to go back to the store. I went back to the store where the store advise me it is not their problem because they have sent it through, I need to contact cancellation. This is unacceptable because the email of cancellation does not get answered either.