discrepancy in home loan interest rates

My Employer UNISA recently appointed Standard Bank as their corporate banker. Standard Bank currently have a marketing drive among UNISA emplyees. A Standard Bank representative visited me in person in my office and promised that the discrepancy in my 2 bond account interest rates would be attended to, which never materialised. I have 2 bond accounts with Standard Bank, one at a 8.55% interest rate (bond registered in 2009), and the other at 9.75% (bond registered in 1995). I contacted the Home loan call center this morning and was told that Standard Bank do not renegotiate on the interest rate of Home Loans. If I am unsatisfied with the discrepancy in my interest rates, my only option would be to move my bond account to another financial institution. I also have 3 bond accounts with FNB. Last year FNB renegotiated the interest rate on the 3 bonds without a problem. Bad customer service from Standard Bank, compared to FNB!