Hi meehill,
Thank you for reaching out to us here on the Community.
I am very sorry to hear you are having problems upgrading your contract online due to the system advising of a balance on the account.
This may just be a system error but we would recommend giving the team a call on 789 or 0345 600 0789 to have this checked. They will be able to view the agreement and confirm the payments are up to date. Once this is done, they will also be able to process your upgrade.
Please do let us know how you get on.
Thanks
Nat