Problems with crossed hot & cold water lines on shower
Demand the manufacturer's instructions so you can review them. Then respectfully insist that the plumber (who you paid to install it correctly) return and make all needed corrections. It's not right for the plumber to expect you to do anything unless you agreed to up front.

He should be correcting the piping if necessary, he should be adjusting the temperature stops, he should be adjusting the cartridge, he should be ensuring the trim is oriented correctly.