Wrong contract

I’ve seen a similar post on here before. I agreed to a new package over the phone with Virgin for £28 a month an increase from £22 i believe it was before. ( I called as my contract expired and they said it would go up to £51 i believe)

Anyway I agree to this over the phone and I’ve since been charged £51. I’m told that that’s the contract I agreed to. I’ve checked and they did send a contract over for higher amount i didn’t check at the time. But without a shadow of a doubt I tripled checked and agreed to £28 over the phone. I’ve been passed from pillar to post over the WhatsApp service and no one can help. I’ve just been told if I want to exit this contract I have to pay £669.08 early termination fee. I don’t understand how they can get away with this. No one I’ve spoke to can help and they just say well you got emailed the higher amount and the entire conversation/deal agreed over the phone means nothing.

can anyone assist