You should have an order confirmation which breaks down the cost of the package, does that match up with what you agreed ?
If it's your bill that's higher than expected, it will break down the charge, any change during a billing cycle will see you refunded the previous package, then you get rebilled from the next package start date, if there was new equipment there will be a £9.99 postage fee, it's normal the next bill can vary but future bills will be as normal.
If that still doesn't help, billing and sales can be contacted on 0800 800 150 to investigate further.
