MTN chase long standing clients away

I have been a client of MTN for 29 years -it means nothing to them -I was offered an upgrade from MTN I signed the paper work as I do every 2 years and retuned , they now advise that they will no longer be purchasing the hand set promised and i must pay more for a different handset - is this how MTN does business- quite disgusting and shameful - their staff don't care. I was advised i could take my business elsewhere