Netstar - Incorrect premium confirmed.

I have been a customer for 3 years now and needed to cancel as my vehicle was being sold and the new owner did not want to Netstar contract. I cancelled but a few weeks later the potential buyer changed his mind. So I called Netstar to take a month to month contract as was quoted a lower amount. I was told that the new amount was going to be 'x' however when I called in again, a higher amt was quoted. I am unhappy with this service. Please can someone senior contact me.