Wrong debit order

I had a unit installed by cartrack in my vehicle on the 4th of May and i was informed that there will be a pro rata which R7.00 a day calculating from the day of installation to the next debit day and i gave them 25th to be my next debit day therefore the pro rata was supposed to be 7x24=154 however cartrack is insisting to overcharge me they went in my account to debit R198 how come while it’s supposed to be R154 are they running a business scheme by robbing their customers? Because Kgothatso and I calculated the amount that if the unit is being installed on the 1st then the prorata will be R175 and it was installed on the 4th i want this to be rectified immediately because im going to take my complaint to ombudsman they must pull up the recording and listen to that call and not mess up with the wrong person otherwise i will make my demands as a consumer because i was misleaded.