Poor Customer service

I went to cancel my contract in august they told me in store end of September will be my last payment, i filled in the cancellation form. In October i was billed again I phoned the store to find out what is happening the person I spoke to couldn't answer me they just said it was captured but was never put through for cancellation, what i don't understand is how that is my problem and why should I pay for their error. I left my contact details for the manager to phone me till today the manager or anyone from the store did not contact me regarding this matter. I phoned the store today again and spoke to the manager who has no way of speaking and kept speaking over me and raising her voice, now I find out they apparently do not do cancellation in store anymore since august I was suppose to phone the cancellation department. My problem is I went to the store in August to cancel the contract but nobody at the store informed me of this and now I must pay again at the end of November for a contract I cancelled in August already because the in store staff didn't give proper information because they were too busy playing with their cellphones. Then what is the point of me going all the way to the store to do the cancellation if I could do it over the phone. Please train your staff on how to deal with customers in store and telepathically especially management who has no telephone etiquette.