Not happy customer

Bad service. I had a pocket router for more than 3 years paying R190 for data, i received a call from one agent and i was told that they have a special i will be paying R169 for the same amount of data and i agreed. June they debited R169, July they debited R411 and on my statement it said once off subscription fee, now I received a statement saying they will debit R505 for subscription. I call the customer care i dont get any assistance. Why do you have to change once off subscription every month and its going high why????