T-mobile t&c changed can I cancel contract?

dbs

Recently bought 2 t-mobile phones through forward cellular awaiting cashback.
T-mobile have sent me notification of changes of terms and conditions but they have not enclosed attached information leaflet as stated in the t&c booklet so no idea what changes are being carried out.
If they increase charges above the RPI or change the t&c to my material detriment I think I cancel my contract and keep both phones without any penalties is this true?
Also will the clawback be inforced on the cashback bearing in mind I would be cancelling the contract due to their rule changes.

If I could cancel the contracts and keep the phones that would be great keeping the cashback would be even better as I would be in profit from either option.

omega27

I think the changes are something to do with using your information for marketing purposes & you have to opt out now. So not really your detriment, so I doubt you'll be able to cancel.