MTN DEBIT ORDER ISSUES

So i upgraded a contract with mtn recently. out of the blue i get debited way more than i should have been debited. After days of trying to contact people i am told that it is a device fee for my new device even though i sent them the contract documents stating that there is no fee's applicable. After uqestioning it many times the agent just says it is a device fee and sends me a survey request. This is not the first time i am havin this issue with MTN. They just take out money from your account without even a notification or anything. I cant wait for all 6 of my contracts to be up with them so that i can take my business else where,