SIX MONTH PLAN

I am trying to find out why they are not billing me according to my six month plan. My first call was on the 23.04.2015 at 16:30 spoke to Nokuthula who was not helpful but rude said that it would be rectified in May which is not the case. The last call was on the 18.05.2015 immediately when i got my statement at 17:45 spoke to Sanele Mthembu who was not explaining to me properly and i tried to make an example with the purchase i did last month which was supposed to be spread over six months but it was not happening. I told her that i am sorry because i am going to lash out my frustration on her but anyway we did not conclude well. All that i am asking for is to understand how their credit facility works as it is not making sense as i work on a budget and this affects me.