Unexplained deductions

I have been using avis mini lease for the past 6 Months. I always pay on time in fact they don't even call me call in to give the kms of the vehicle so that avis can deduct my account. January 2015 I was deducted the R8900,00 and a week later deducted a further R5900 leaving my account in a negative this was done with out my consent I contacted avis centurion and was told that they can't see the problem and I should bring in bank statements I did that and everyday since I keep calling them an keep getting told that the manager is looking into it. Avis seriously please sort out my account and conclude what you are looking for because this is ridiculous, frustrating and concerning as I trusted this company and always have used avis. I have a lot of family and friends that use avis and they will not be happy after hearing my incident. It's taking up my time and money witch is effecting my life.