MTN One-sided Contract Change

After being a very loyal customer of MTN since 1995, I was absolutely disgusted by the manner in which I was treated. I have three separate cellphone contracts with MTN one of which has been in existence from 1995. The aforementioned contract currently constitutes a monthly payment of R500, in exchange, I receive an allocated amount of Anytime Minutes, SMS's and Data. On the weekend of the 16th of June I was busy making an important call when suddenly my call was ended and I was told that I did not have any Airtime on my phone. This was very shocking as I have never had an airtime-oriented contract. After this I went to the local MTN branch and was told that my contract had been changed and thus I only recieve 100 Anytime Minutes each month and when these minutes have been used I have to buy airtime. This is a clear example of breach of contract seeing as they changed the essentialia of my contract without my knowledge or consent. Upon a query I was told that MTN has done this to every contract yet my other two contracts do not have this problem.<br> <br> I am utterly disgusted and humiliated as a customer and clearly the CPA is of no importance to MTN!!!