Seems like they remove the prepaid numbers at regular intervals, then you have limited changes available monthly to update them. Guess it's a workaround to enforce the rule
I think guys were reselling smaller data bundles to mtn prepaid users, especially with 25 numbers and unlimited changes. The price difference per gig probably made it viable.
I suspect this is likely due to informal reselling.... cant see how it could have been abused any other way. So........ what is the cheapest postpaid option to use to work with the new rules? I will upgrade my sims to that if its cheaper than using prepaid data