MTN CUSTOMER SERVICE UNACCEPTABLE

I have been receiving my statements and invoices by e-mail from MTN, until around Jan 2015, and they just stopped sending the documents. Each month since Feb 2015, I have had to call 808 to request the documents to be sent to me. Each time I call, I'm told that I will receive them in 2-24 hours, which never happens. Only when I call the 3rd or 4th time, and demand to speak to the supervisor, then do I receive them. Needless to say they always refuse me to speak to the supervisor. I have requested my latest documents for the 2nd time, on 18 May, and 3rd time on 26 May 2015, and as usual I was told 2-24 hours, and I still have not received them. I may not make a difference to the massive revenue stream of MTN, but i still deserve better service. I am expected to pay my account monthly, ON TIME, but they cannot provided a timely SIMPLE service to me? I can be sure that I'm not the only customer frustrated by this.