PAYING FOR SOMETHING I NO LONGER HAVE; VERY VERY ANGRY

Tracker, one of the worst service deliveries around, My car was sold, i called tracker to inform them that the car has been sold and that i would i like to cancel my contract due to me not having the car anymore, i send a canceLlation letter as i was requested to do. I called again to find out if the letter was received, i was informed i needed to send it to another email address after sending the letter to about 10 different email addresses i called again and was told no letter was received. again i emailed, to this date almost 2 years later i get a call from debt collectors informing me that my tracker account has been handed over, so i called and was told we agreed to a 5 year contract and therefore cannot cancel, i mean now seriously which hole do i look like i crawled out of, would i be that stuipd to agree to a 5 year car tracking contract, WHY AM I PAYING FOR SOMETHING I NO LONGER HAVE. During the time we did have tracker NOT ONCE DID I GET A CALL FROM TRACKER asking if the device is working fine or calling to find out if all is ok NOT ONCE. I WANT THIS CONTRACT CANCELLED I NO LONGER HAVE MY CAR.