End of your 12 month discount?
Call the broadband team to renew and get a new deal. Make sure to be signed in to get the number.
Why did it increase, as above: end of a discount period/minimum term offer.
And as you failed to check your emails or keep track on your subscriptions and the end dates of any discount periods/offers this has come as a surprise to you.
If you didnt receive an email then it could have gone into your emails Spam folder, again you should check this and ensure it is correctly set up, or your email address that you provided when you signed up is out of date as you have failed to keep your details up to date