Night Express data bundles purchased but no value

I am a regular purchaser of the MTN Night Express Data products. I buy the 20G for R360 that are suppose to expire after 60 days and the 1G for R10 quite often. For the first 2 months I enjoyed the service with no fusses at all. Since then MTN has been as nuisansecal as the nightmare its become to deal with their so called service champions and supervisers at their call centre. Now what happens is I will connect to the network,then after a couple of minutes I get a message on the browser saying I`ve run out of funds I must top up to continue browsing and yet when i check the balance I have 16GB remaining on my account. As for the daily night express bundles some I`ve had to forfeit and some I was refunded because of the same thing - being kicked out of browsing for having run out of airtime and bundles only to find that I have a positive data balance when checking. I could write a book about the many different speculations on the cause of this hellish inconvinience. I also have a couple of reference numbers which were a confirmation of escalations . Needless to say no feedback has been received as yet. I`m so frustrated I`ve actually gone numb