Unable to get answers regarding account charges

I upgraded my MTN contract in April of this year and ever since then been billed exorbitant amounts, which I can not understand as I do not receive an itemized statement. I am supposed to have 100 minutes and 300mb of data per month. I went in to the MTN store at Liberty Mall for assistance on 01/08/2015. Upon explaining my predicament regarding the high charges. The lady says to me that I am using too much of data and making too many voice calls and suggested I cap the account which I agreed to. I then asked her for an itemized billing. She then said that she does not have access to my account and can not give me such information and that I must contact 808 the customer care number for the bill to be emailed to me. How then did the assistant know that I had gone over my limit? I decided to check my usage myself according the my device logs and apart from April I have not exceeded the minutes and only used 175mb extra of data in June and 55mb in July. I then tried calling 808 and keep getting cut off. I have tried registering on MTN active to view my bill online but the OTP sms is not sent to my cellphone and I am unable to log in. I need answers.