This is brilliant!

A question. I have an economy reward flight booked through my account. I don't have enough miles to upgrade it to PE, however a family member has enough miles in their account to do so and is willing to upgrade my flight.
There is PE reward space available; should
they call Flying Club to upgrade my flight or can I contact them myself and give them the family member's details for confirmation? I ideally would like to make the change and pay the extra taxes myself, and not have them pay for it (just inconvenient)
It would save the £7.50/1000miles transfer fee which certainly adds up.