MTN data contract

I have a data contract with MTN which is capped at 50gb and for first six months I've been credited with 50gb of data on the 25th of every month without delay and if there was leftover data it wouldbe carried over to next month. Data was capped because some months I would finish the 50gb and be told I don't have data and wouldn't connect. After six months they MTN uncapped the data without my knowledge and changed the dates of crediting me with data to any date after the 25th of every month and leftoleftover data is taken away on the 25th, then you start incurring extra charges until they decide to send the data you paid for. This is **************** because your data is supposed to be carricarried over to the next month. But you loose it before the month ends and you are charged twice. ***