Disappointed in MTN

At rhe end of last year I decided to change to another contract. I still had R690 airtime left and did not want to loose it. The decision was based on if I can carry it over or keep my contract untill I used the R690. I was told that I could carry the amount over and went ahead with thw new contract. After 3 or so months the airtime disappeared and I logged the first complain. The said that I should have been rold that the aitlrtime would expire after 1 month and that did not happen. After this they asked a Team Lead to call me and he did. He advised me to go to the MTN store where I got the new contract. The store opened another complain and send me the reference. Yesterday I got an SMS stating that the ticket was resolved. Nobody phoned or even send me an sms with the reason or outcome. I phoned MTN again and the answer was that the policy is that the airtime expire after a month and I should except that. I can except the fact that airtime expire but if I was told that I would have waited to take on a new contract. This for me is dishonesty from MTN's side and for me it feels if they ******* me in a contract just to make their targets. Not satisfied.