Bell Canada complaint: after cancel the prepay phone, Bell continuedly to send letters ask for money

I buy the prepay cell phones(4 Sim Cards) from Bell Canada for one month and then I phoned them to cancel them. They told me no worry. it is cancelled. two months later I got a letter to let me pay the other money and told me that my phones are suspended. I did not want to argue with them and I talk with them if I pay the money Bell will completly clear my account, they say yes. I paid the money. one month later, I got another letter and let me pay. I call back Bell say it is the resume fee. I talk to them and last time I pay bell for cancelation, why Bell continuedly ask money, Bell representative check the file and say it is recovery fee. I told them it is ridicules. Finally bell said your cell is cancelled and you have $2 credit in bell. you do not need to pay any thing. Now I got a letter form Bell collection, let me to pay 238 dollars.
I do not understand how bell to operate, client use one month prepay phone, Bell insistently ask for the pay no matter how many time you call back to explain to them