Bad service

I have a personal loan with FNB for R151 000, i paid R85 000 lump sum to that personal loan. I contacted personal loan department to reduce my monthly instalment. They said they will call me after two weeks to inform me about my current adjusted installment. FNB didn't contact me at all as they promised. I checked my personal loan detailed balance statement in my online banking app and saw that on the 26 th of October my payment installment is supposed to be R1680.03 but FNB deducted R2232.89. When i call they send me from pillar to post, i have spent more than R100 on airtime because they are sending me from one department to another. And this is not the first time i encounter something like this with fnb. I am so frustrated and devastated.l