So he called them up after receiving the high quote?
In that phone call he advised them he wasnt going to go ahead with that quote
What needs to be understood is the conversation after that. The advisor should then of gone through the options of how to cancel - ie not proceed with the new quote
Your brother is allowed a copy of that call...he may have to pay a small fee - normally £10. If he wasnt advised how he needed to cancel the policy, when he has clearly stated he doesnt want it, you can use that as levarage..they will have a complaints team, he needs to go to that dept now