When you do flash design, you don't give away your original .fla files, but only the .swf files. When the client requests the .fla files, they will have to pay for that in addition.

Extracting a .swf file to a .fla with pix, actionscript etc. is possible, but I don't think it's right with respect to the original designer.

Maybe, the representative has to ask (and pay) the original designer for the .fla files. Then you can continue your work.

Just my thoughts.