**** and Incorrect billing

I bought a bedding which was costing R999 on the 13 February 2020 and the order was delivered. On the 23 of February I made a payment of R500 and I got an sms that my balance is R872.03 and today I received a statement saying that my balance is R903 . Where is the other money coming from? I cannot wait to pay off the their money and close the account.