Very bad service with ******** staff

I had a car track account with a company call Car Tracker. 2022 i decided to cancel my contract with them. Upon my cancelation I was charged cancelation fees and and I had to pay for 3 months arrears wich costed close to 5k.i paid that and demanded a paid up letter that was 2022 September. Car tracker never stopped calling me claiming I owe them, they never stopped debiting my account and I had to reverse all the time until they handed me over to Nimble. Nimble has been calling me and sending me emails and when i tell them I had paid up that account and they would tell me to send a paid up letter and I have sent it more than 20 times since early 2023 till today they still harrasing I'm so tired of these people pleaee help me