Plumber unable to replace Moen shower cartridge
Maybe it's me but I would try to pull it myself. Sometimes they're difficult due to corrosion and scale buildup.
Once you have the cartridge puller and with the water supply turned off spray some Limeaway or other decalcifier on the cartridge. Let it sit for a bit then give it a shot. I haven't had to use a Moen puller but I doubt that if used according to instructions it could hurt the valve.