vivint security apex security I cancelled and then they still billed me any way and did not send a notice of renwal , Internet

I called vivint a year prior to my five year contract ending and paid off the balance and asked that they cancel my service. A year later I started getting debited again. So I called and asked for my money back for the last two months which they had debited me. they told me I should have cancelled in writing. however when I paid in full a year prior to that the person on the phone assured me that I was canccelled and no further action was required. The contract does state, now that i have read it, they require written notice. However it states that 60 day prior to renewal I will receive written notice of renwal. which I didn't. Three things: !the sales man that origianally sold me the equipment said that they ad a satifaction guarantee. 2 my system had never worked and the installer never installed a sensor on  the back door. 3 I didn't recieve notice of being renewed and I cancelled a year prior.  I cancelled my home phone a year and half ago and vivint has not been able to reach my house unit the whole time. They absolutely knew I was cancelled or they would have tried to contact me. At least send the police by and see if i was alive. Beware of this lengthy contract that you can not get out of whether you are using this service or not.