Hi joemoodie
Welcome to the community forums.
Sorry to hear you've not been able to get an answer to your query regarding your new contract and how that might affect your new bill.
Once your new contract activates, your next generated bill will show this change and any prorates from the two price differences from the old and the new contract ( if there is one ). As you pay in advance for your services, you might find that the previous bill covered dates after your new contract will come into effect. So you'd see those dates reflected on the next bill as a prorate, either a further charge if the new price is higher or a reduction if the new package price is lower than your previous monthly amount. It's not a double bill just the one bill that will show the changes that have occurred.
Please let us know if you are having any further issues or have any questions at all. We'll be here to help on the community forums if needed.