Onecom mobile contract

FFHillbilly

I was cold called and offered a sim only mobile contract from Onecom, at the time they said the contract fees were £10 per month, there's no mention of VAT on the contract but I asked at the time on the phone and he said yes it's £10 plus VAT per month.

what I now realise is I pay the full amount £37.75 + VAT to Vodafone (£43.50), and then Onecom credit me £27.75 to my bank account. so the total per month is £17.55 and the contract length is 36 months
they seem incredibly difficult to speak to once you have a contract, every case I raise in the online support centre takes weeks for a reply and they just spout some rubbish about discount length and refer me to the vodafone billing section,  and close the case
who can I take this further to?