Lost data

MTN migrated my number without any warning from student contract to prepared. I was advised to re-register (Rica) my simcard, for it to be active again. By doing so I forfeited my data bundles, but I got my airtime and points back. When I asked why, I was advised that my number is now recognized as a new number so I forfeit all my balances. Which is not true, because I got my airtime and points back, and say, it is true that I forfeit all my balance. Why didn't anyone inform me about the migration. I would have bought a month Data, that would be forfeited within 2 days