Not Allowed To Close My Account

I installed a tracking device on my vehicle in 2013 and never defaulted on my account. In January 2015 I traded in my car where the device was installed. I have tried to close my account with Altec Netstar since then without any success. I sent an email to cancel the account in Feb/March last year they never responded. They have continued to bill me every month for a car I'm no longer in possession of. In November 2015, I called their Customer service dept. seeking to close this account but I was told that I can't close the account cause it's a 36 month contract. I told the consultant that I'm not aware of such and no one explained that to me when I opened an account with them. I requested copy of voice records of me agreeing to such, since today I have not recieved this. And they are continuing to bill me. This is pure day light ******* since I'm paying for car that I'm no longer in possession of (for a year) and I'm not being allowed to close off my account due to shady dealings. My right as a customer has been violated by Altec Netster which in contravention of the Consumer Protection Act. I have lost about +-R1900 (R163*12 months) due this. I want to be reimbursed.