We know that this occasionally happens and there are ways to fix it without having to remove the tiles from the wall and change the piping.
Here is how: The first solution would be a reversing block which reverses the supplies within the block itself. This installs between the iBox and the brass valve itself but please be aware that it may reduce the flow of water slightly.
The second solution is a reversed thermostat cartridge which will reverse the supplies within the cartridge itself. This is only available for shower valves that support our 98282000 thermostat cartridge.
The third solution is to reverse the ID's on the escutcheon plate. This reversing face plate has the flow control at the bottom and the thermostat at the top. To do this you turn the water off and then remove the brass block from within the iBox. Turn it 180 degrees, upside down and secure it back in place and then put on your new reversed ID plate.