Damage of my Credit rating

I app**** for motor vehicle with Mi Way, as they gave me the quote they told me to take car for inspection before they can cover it. I asked them that as soon as I took the car for inspection I will contact them to start the monthly deductions. I did not go due to work commitments but they continue deducting the money in the bank which I did not give them a go ahead to deduct as per our telephonic conversation. Now my credit rating is affected because they did not find money in the bank. I contacted them to write a letter that must indicate that they deducted money before I could give them a go ahead. I spoke to consultants, they gave me the Ref number as *** and the person promised to send letter before end of day. 2 days passed I called to enquire, the lady that assisted could not track the reference number, she said she would arrange for me to get a letter and gave me ref number ***. Up to now I did not get any feedback from MiWay. What should I do to get this letter so that I can update my credit ration??? I am so disappointed with MiWay. I do not regret cancelling the contract with them since there are many insurance companies out there who know what a client is.