bridge of contract

I entered in a an agreement with tracker to install a tracking unit on one car and activate another tracking unit on my second car that was already installed. We agreed that l will pay R398 per month for two cars. We agreed on record that there will be no other charges, no istallation fees. On the 25th of May 2015 tracker decided to debit R2093 from my bank account which constitute bridge of agreement. This act has impacted negatively on my budget, consequently incur charges, l want tracker to refund my money with immediate efffect before 1st June 2015.