Bad service

I have a Flexi reserve facility with ABSA home loans.

I asked for a better rate with ABSA since my account started with Trust Bank years ago.

They gave me a rate of 8.98.

Unfortunately my monthly repayments don't correspond to this so called new rate given. It is actually more.

I am constantly in contact with my personal banker, which also doesn't come to light with proper answers on why they charge more than the expected repayments?