Misleading clients

last year i got a call from Vodacom claiming that im paying more because im on an open line contract and told me that i can be moved to a top up line to same money and was told that i will be paying five hundred and something, i cant remember the exact amount but to my surprise i have now paying nine hundred and something which is way more than what i was paying on an open line, i was misled into saying i will be saving but inserted im now paying way more. I called in January and was told they will log a case but to my surprise that did not happen as well. I then followed up last week but was told that theres no case logged. i am really disappointed in the service i have received in the years i have been with them.