The initial contract (landlord/tenant situations excepted) is for 12 months with a 3 month notice period. That effectively means a 15 month contract in the first year.
After the initial 12 months, the contract is ongoing month by month still with a 3 month notice period.
That means that should you wish to cancel after having the service for 2¼ years you would only be tied in to the 3 month notice period and not 9 months as you would be with BT or most other service providers.
If the reason for cancellation is moving or selling your home, Gigaclear will transfer the service to the new occupier without holding you to any termination period.