ABSA HOME LOANS - NOT CONTACTABLE - BEING IGNORED

I have been trying to get a response to an email I sent on 17 Feb 2020, as ABSA is overcharging me on my Mortgage Loan. It would seem that with the recent reduction in bond rate has been ignored by them and they are still deducting the old amount. I initially received a reference number but that's it. Email or telephonic attempts are not working. How do I resolve this... If it was the other way around, they would be slapping interest on my account without blinking....