MTN system and lack of service unacceptable

I'm not sure whether this is happening to other customers, but for the last couple of days whenever I exhaust my data and airtime surfing the net via the MTN network a blocking window begins to pop up whenever I try to open a new tab, telling me I have no funds and preventing any further browsing.<br> Fair enough, but after loading airtime using their Easy pay (whatever) system and converting airtime to data and verifying that the airtime and data reflect in my account using USSD messages, the blocking window continues to appear and prevent any further browsing for about 40 minutes. <br> MTN's online store (which curiously can still be accessed during this period, ostensibly via the internet as there is an \https"tag in the URL) claims that recharges are practically immediate"