Bad Service From tracker

Recently had a car accident and my car was written off, I called tracker for my policy since I had you insured me tracker device with them , however everything turned into a nightmare my account was debited twice after I requested for the policy to be cancelled. Due to their incompetency I had a debit order that bounced and was charged for that. I was advised that I will be refunded. A week later I receive an email that I need to send proof of banking, which doesn't make sense to me since they have been debiting. I am unable to go to banks because I am not well. Why should I suffer for their mistakes? I am really not happy with their Service ,after 5 years of uninterrupted payments. This is disappointing.