poor service in the homeloan department at FNB

I have a home loan with FNB and want to reduce my monthly instalment but do not want to reduce the terms / months remaining in the home loan contract, now I called FNB homeloan department but could not get any assistance with regards to that, they said an SMS would be sent to me till now it hasn't come through and what I really want is a simple calculation but yet I cannot get help, this is really poor service especially from one of the biggest banks its really disappointing.