betterbathrooms

Anyone know anything about those built in the wall showers they sell, A customer has one and the shower temp is not controlable, Its been in about 7 years, All you can see is the chrome plate and knobs, I'm assuming the plate and knobs will come off but can I get the thermastat out or are they non serviceable,
I don't want to start on something thats going to end up changing the whole shower valve because the whole wall will need rebuilding,
So anyone done one,
thanks