Broadband upgrade not showing on account.

midge101_2

I have 30 days left on my broadband contract with Virgin media and I logged into my account and I was offered the same price to continue for another 18 months at £24 for 125mb. I have had problems with my wifi so before I agree to the contract I rang them up and asked for a new router. They told me I cant have one until I upgraded and luckily I saw on my account that it was only an extra £2 a month to upgrade to 250mb for £26. Which I agree and I was sent the pre-contract documents. When I received the router I was told when I have activated it my account will show the upgrade with the new package and price. But it has not it is still at the old package and price and now they tell me they can't adhere to £26 a month. I can have the upgrade at £33 a month. Are the pre -contract documents legally binding? Does Virgin media have to adhere to this?

Any advice would be helpful thanks