Well I searched around the Internet and found that the cellular settings are on the main page of settings, not under general.
Double check your account settings. Make sure they are correct with what you know you have set up with the cell company.
One of the things that I have been seeing is people having to call their provider and get some kind of walkthrough. The typical stuff about restart your iPad, turn off wifi, check for connection, turn wifi back on, etc. they might do something on their end with your account and then ask you to Reprovision your account, "Reprovisioning the account can be found SETTINGS>GENERAL>RESET>SUBSCRIBER SERVICES>REPROVISION ACCOUNT". That is the thing that seems to get everything back up and running. I don't know If the cell company has to set something on your account on their end for you to Reprovision the account on your iPad.
I would give them a call and see what they can do.