Debit order

i have a problem with vodacom when we go to store for a complaint we didn't get the right answers even if we make calls, the problem is that the contract that was signed for was for an amount of R199 but on December we did pay on the 16th R495 to that R495 , R295 was for November with Arrears So R200 its for December and we did pay earlier, and the next problem is they did try to deduct month end of December but we did pay for December cash on the 16 and now they did bill us not to get the money for December on the bank and now we must pay the arrears but we did pay for the month on January they did try to deduct R508 and i don't get it , the money was supposed to be deducted is R199 and the was money on the bank but the didn't take the R199 so to me they are over charging us .