Vodacom in breach of contract

I have a contract with Vodacom. They suddenly change the package I am on and want me to pay extra money for the 150 data they give. What they don't tell you that is that you do not get the 450 sms bundle any more that you already paid for and have a contract for 2 years. I phoned them and they informed me that someone will phone me back. After a week i received a sms that my query has been resolved. ??? No one phoned me and I only get this computer based call stating I must pay the additional cost for the contract. When I am going on the Vodacom App on my phone the amount is still the amount according to my contract. Vodacom is in breach of the contract I have with them. They cannot just changed contracts and expect customers to pay. Vodacom doesn't come back to the clients when inquiries are made. This is very disappointing because I am with this service provider for years. I can now understand why customers is changing to MTN.