Debiting more than amount on policy schedule

The current amount which is stated on the last policy schedule we received from Oneplan states that the amount to be deducted should be R3113.47. however my account was debited with an additional R36.03. I sent an e-mail to ask why this has been done and the smart call center agent Lorraine Mmopelwa tells me that this is the new premium amount because that's what it shows on the customer statement. so is it just fine for one plan to debit random amounts from my account monthly? Can I please have proper feedback on why we are being charged more than whats stated in the policy schedule. and please hire more intelligent staff to work in your call centers, customers should really not have to deal with *********** staff.