Vodacom - give me the wrong phone and then simply ignore

Vodacom Retail Park is probably the worst Vodacom store I have dealt with in 20 years of being a Vodacom customer. I re-newed my contract, I was given a phone with half the storage capacity as the contract i signed. I went back and notified them that its the wrong phone. They said they will order the correct phone. After numerous calls for feedback, I went into the store to be told there is no stock of that phone in South Africa and they can't exchange because I have used my phone (the phone they incorrectly gave me). They also downgraded my contract to the smaller storage phone without telling me. The contract isn't signed, but I am being billed for it. No accountability for their mistake and they just hope the customer will disappear....