This should be a classic case for the Ombudsman Service. Let's look at facts as reported by the OP.
2008 OP bought an iPhone 3s on contract with (amongst other things) unlimited data.
2010 to current OP has opted not to upgrade and remain on legacy tariff.
(Note OP could if they wanted and if they could afford to do so purchase a new iPhone from Apple direct and use existing tariff keeping same number).
2014 (i think) o2 change the terms of the tariff to limit the data to 4g.
Without looking at all the t&c's, IMO o2 MUST have made clear at the time of selling the original contract that the terms of the tariff could change in future. Hiding a fundamental element in the depths of t&cs is generally frowned upon.
So what should the OP do now?
1. Email complaintreviewservice@o2.com detailing the fact they are on a legacies tariff that includes unlimited data.
2. IF o2 believe that there was a fair usage cap at the time then they must evidence this and evidence that the OP was reasonably aware at the time of taking out the contract.
3. CRS will then email their final adjudication which, knowing o2, is likely to be a load of waffle followed by "tough that's the way it is".
4. Refer the complaint to the Ombudsman with full details about the unlimited data and how o2 are trying to remove the service even though you continue to remain on the tariff.
My feel is that the Ombudsman may well side with the OP assuming the fair usage cap was not in the t&cs in 2008.
Oh and if you did lose you can rejoice in the fact that just referring the case to the Ombudsman will cost o2 £300.
Note you MUST go through complaintreviewservice@o2.com for a final determination before you can go to the Ombudsman.
Good luck. Process may take up to 13 weeks but may be worth it. In the meantime if you want to move to a more up to date iPhone you can purchase a new one and keep your existing account and tariff pending outcome of your case. Please let us know how you get on.
