False advertising and billing

I did not pay rain due to lack of funds and when I called to cancel my account with them, they said I can only come and cancel at the office. The lady that assisted me on the phone said the only thing I can do was to completely shut down my router and sim card so I don't use the services and I did that for atleast three months. I finally went to cancel my account with rain on the 25 of July and got a cancellation email but they are still debiting my account and when I my account it says i am owing rain R1857 and I don't understand why because I was not using any rain services for the three months they billed me for. I want rain resolve this because I didn't have R619 and now they expect me to pay three times that for something i didn't even use. On the adverti*****t they said it was not a contract, cancel anytime time but I now see myself under the conditions of a contract.