Refund on interest calculate in advance

ABSAlutely ******* service I was on the call for an hour ended up being frustrated to the point where I could just bang the phone to get assistance from a person with knowledge, My inquiry is simple as interest rates are calculated in advance prior to inception once the reserve bank reduces its interest rates we get a reduced installment (provided the rates were reduced and not increased) my interest was initially at 15.5 and now I'm on 12... my installments reduced a bit so my question to ABSA is did they refund the interest which was calculated in advance? ref ***3 spoke to inocentia mahlangu who didn't know and told me she doesn't know asked her manager who she claimed is Russell Hobb I later found out its Russell boysen who told her that it's automatically calculated on the system, called again Gomotso shame she tried to help me she got Saness (not sure of spelling) who told that there is no refund that needs to be refunded and shes been doing this for 8 year (not that I wanted that information) so all in all no one assisted me with correct information from three to four people. please advise me my installments were reduced due to interest rates decrease but were my account refunded anything as the interest rates were calculated in advance? if I could rate you guys a zero I would