Interest rate on personal loan!!

I app**** for a loan at one of the Absa branches in East London and I was not told that my interest rate is not fixed and was never given a option to say what kind of interrst rate I want and now that I have taken the loan i noticed that my instalment is changing every month and now I am being told that my interest rate is not fixed and they cannot change that and during the loan process I was never told of this kind of interest rate.

I want my interest rate to be fixed because if i was given the option in the beginning that is what i would have chosen.