I want to make several changes to an upcoming reward booking (adding a US domestic connection both ways, changing the date of the outbound flight, changing the routing of the inbound flight). This all has to be done over the phone (since it's a phone booking). Will I get away with paying just a single change fee of £40 or will it be charged per change? Or is it one of those things that depends on the mood of whomever I get on the phone?