You cannot put up prices having a binding contract

We sign a contract having agreed to a price and terms for 24 months Vodacom advertised saying 24months that will be the cost now suddenly you Vodacom wants to change it it is breach of contract and there for i can cancel it .We can not pay more for bad service you say you Vodacom is the leader best waiting 15min for your call centre to answer my call that is bad and unacceptable service that Vodacom reception connection on 3G is so bad you cannot stay connected for more than 5 to 10 minutes at a time that is ridiculous and now we must pay more for your vodacom **** **** ****!!! NOOO NO !!!!!!