Debited thrice

You guys are supposed to debit my account once every month an amount of R99 on the 21ste of every month however this month you took money twice on the 18th and today again making it three payments. My account was not in arrears because the last payment I made was last month, I’m not sure whats going on can you guys please refund me the two payments because the bank said they will charge me R81 to reverse each amount