Sim only plan

[Rb1]

Do I need to stay the full 12 months with a sim only plan

[Bambino]

@Rb1 The answer is no, but you would still be responsible for paying any months that are still remaining on your contract. https://community.o2.co.uk/t5/How-to-Guides/Cancelling-your-contract-An-updated-guide/ba-p/1234852

[MI5]

@Rb1 

You can upgrade and stay with O2 at anytime, but if you want to move networks you need to pay it off or wait until the mimimum term is complete.