What a ripp off

I took out a contract with Vodacom on 24 April. The contract is for R99 per month or so it is supposed to be. I have also put a cap of R50 on the contract, but today a received a bill of R744. I phoned their call centre today and they informed me the contract is not capped, but the thing is I went into the store and the person that helped me showed me on your system it was capped.