Upgrading plan when on 12 month airtime?

[Alec2]

Hi, I'm about to get the 30gb sim only plan for 12 months, however my data requirements may go up and I would like to know whether I have the ability to upgrade to the 100gb plan during the 12 month period.

Thank you in advance.

P.S. would this mean that my new plan is extended for a further 12 months from the upgrade date?

[madasaf1sh]

@Alec2 

You can only change to the plans that are available in myo2, under upgrade and your contract doesn't extend. 

However if you want to change to any of the uSwitch deals then you would have to pay off your current contract.