unhappy customer

I totally regret taking a contract from vodashop Mafikeng, every month they deduct R500 from my account but I only used the phone for two weeks now it's heading towards month end another 500 is going to be deducted for a phone I don't even have. I took the contract on 6th of February used it until the 15th because the battery was always low, I got another phone on the 24th but it didn't read the sim I took it back, when it returned there was a button missing, when Iwent to report it the manager accused me saying I removed it they booked the phone in on the 26th till today.