Duplicated billing & 85 days waiting for a refund so far.....

An issue with the billing was identified but the reason why that happened wasn't provided and I was informed that there was an under collection on cartrack account to which I requested an opportunity to be guided through what product I am subscribed and how much to which instead was followed with a letter of demand and I settled the outstanding amount to avoid the long going harassment from the agents and after that the amount under collected was force debited from my bank account without any authorization from my end as I had settled that outstanding amount which has left my account with Cartrack on a credit balance. I have been waiting for refund for plus 85 days after being notified it would take 7-14 working days and at this point have exhausted all resources possible to get a refund without any success.