Limits very conveniently never set

I recently renewed my the contract my son is using on a 500MB data bundle, and the consultant from the MTN outlet in Waterfall Mall assured my TWO TIMES that the number is capped / limited, and that once his data bundle is depleted he will not be able to exceed his monthly spend. When I queried my account due to the high cost, I found out that the limit was set but the field was left blank, thus in effect no limit was being enforced. To make things worse, I could not pick this up sooner or take action as I was not receiving my invoices or statements. After numerous attempts over the past 3 months MTN was unable to send me my account statement or invoices. I have logged 3x seperate requests, and followed each of them up on a weekly basis but received the pdf documents I requested, only a nasty surprise when my debit order came through