Bad company practice

I had a tracker device fitted by Telmatics, I advised telematics to cancelled my account as I have sold the car. They didn't and kept on Debiting me, I reached to them and there was no assistance. I reversed the debits, Telematics sold that account to Nimble, i have been battling with them for over a year now. They said I must send all emails sent to Telematics and they will investigate, the lady I spoke to her name is Tyra Everts. She promised to get back to me and now she doesn't even respond to my emails. They have listed me for an account I don't owe. I am frustrated with this company.