My man dxb flight is sold out 22 on the 15 sept in j

I'm currently waitlisted for j but unless a seat appears I'm stuck in y. How easy is it to get hold of the purser to ask to do an onboard double upgrade?

I mean in j or f the purser is around but don't see them when you are in y! I can imagine getting into my y seat asking to speak to the purser and them ignoring me and not bothering to even come over! I'd also rather get it done before take off!