MTN forced contract changes

So I have been on a contract with MTN for 24 months where I have had 40gb data and 100minutes. I have paid all 24 months without fail. A few days I got a message to say my contract had expired and I would be on month to month( meaning the terms of my contract do not change). Today I get a call to say the data portion of my contract will fall away- and I would be paying out of bundle rates.!!!To my understanding, contractual terms do not change with month to month.... I am disappointed in MTN and the service - or lack thereof!