Twice. Once on UA from Y to J when the obnoxious pax behind me put their knees up to prevent me from reclining, and claimed he has no leg space and wasn't doing it on purpose. The FA immediately saw through the BS and moved me to J.

Another time on CX, but just from Y to Y+ (definitely not complaining though), after I had given the FA's some chocolates on a HKG - SFO flight right after Christmas.