Increase in installments when interest rates go down.

Standardbank is frustrating me. Earlier this year i logged a queries with them for increasing my home loan installment even when interest rates go down. To this date it has not been resolved or i have not been called back for.

They have once about increased my installment on my vehicle when the interest rate went up. The increase is approximately R200 per month. i logged a couple of queries which standardbank has not explained or resolved with me but closed the queries. When i spoke to Ndileka Pati ***) she advised that my account which i had paid double my vehicle installment for that month was in areas. She logged a query and promised to get back to me before the end of the day which a week has passed and she has not called me yet.

I once again called Standardbank speaking to Aloisha Ndebele ***). i didn't receive any concrete answer and she demanded that i beg her to log a call for me. I have spent a lot of time on the phone trying to resolve this but no luck and absolutely no sense of empathy or desire to assist from standardbank

My question is why do my installments go up when interest rates are going down.