Rain Increased my premium for the last 3 months

Rain Increased my premium for the last 3 months. I have enquired about this twice now and no one comes back to me. The first time the person said sorry it was an error and they would credit my account, the next month the same ridiculous amount went off my account. This time when I phoned the woman decided to argue with me before even checking my account!!! I asked that I speak to her manager and she said the manager will investigate and come back to me the same day. That never happened. I am absolutely disgusted in the service I'm receiving and the absolute lack of assistance from the call centre agents