Incorrect usage of data and Increase in contract

I emailed MTN [Email Removed] on 26 May 2015 due to increase in subscriptions that was never communicated and todate NO RESPONSE. I called the call centre and they simply say send an email ref ***. Secondly I called twice to query why my monthly data allocation and my purchased data is used up first and then the promotional free data thereafter which means that the promotional data never gets used as it expires before I get to use it. One agent said its incorrect and will get it credited back to me and im still waiting when I followed up on above ref nr this agent insists its correct just to get me off the phone. I checked my usage on my second nr with MTN and the promotional data is used first so that you can enjoy the benefit before it expires and then only your monthly data is used thereafter. I would like this error fixed, im so tired of this *********** call centre and the fact that you NEVER get feedback EVER and they will tell you any nonsense to get you of the phone. I want my expired data credited back and this error to be fixed or I will go to ICASA.