Unexplained R2 increase on bond installment

I received a letter from Homeloans at 12:17am, stating that "Our records show that a transaction has resulted in a change to your home loan instalment, as reflected below" The increase is R2 increase..."The debit order amount for your loan account will change from R11 675.03 to R11 677.17. If you have any questions about the content of this letter, please feel free to call us on ***." I have called this number and the agent couldn't explain to me the reason for the increase and said that he will get his manager to call me.