I had enough with Telkom

I have purchased iphone8 at west gate mall only to find out that the phone is exactly the same as my iphone6. I wasn't told that I can't return the phone when I have the following day and the male manager gave me a BIG attitude they gave me the forms to cancel the contract which I did the same day. I left the phone at the store and was contacted by another female manager who has said she is assisting me with the cancellation of the contract I have send her the proof that I have send the cancellation forms. She had asked me to assist her with to unlock the new phone as it had my password when I was unlocking it. But now the thing is telkom is still deducting every month which is something I don't like at all. I would like them to stop deducting from my account as I don't have a phone with me and I have cancelled the contract with them.