Angry;annoyed;disappointed

I have been a customer with Vodacom for more than 17 years. In February I took out a contract that was supposed to be a R169 Topup contract and was shocked now to find out my balance for this month is R1298.00 ,to my knowledge it should be around R600 with my latest contract.When I contacted them to inquire I was told my latest contract is an open contract.I have in the 17 years never taken an open contract and this contract is for my grandson,why will I get him an open contract when I personally have a Topup contract.I am very annoyed and disappointed with Vodacom.It is my month to upgrade but I think it is time to move to another service provider.I want this matter sorted ASAP or I am going to the external ombudsman.