Incorrect amount deducted on my account

On the 20th of November I took extra contract with MTN and the instalment would be R199 of which the other one I was paying R194.01 for ***) so when combined I would pay R393.01 but on the 20/12/2020 R470.30 was deducted on my account when I called and asked why was R470.30 was deducted I was told that it was a subscription that I did but yet again the statement that was send to me shows that R396.18 was going to be deducted I want to know why is it that the amount shows on the statement but different amount was deducted I want my things to be fixed that is why I reversed my debit order because the amount we agreed on was not deducted on my account.