Wow ! The Law really is an ass in this case,or at least a piece of ass.
Seriously that is ridiculous , it should be appealed on the basis their consent was not given with conditions,either directly or implicitly ,consent was freely given. By all means charge him with failure to pay for services but rape,thats not right.
It is a selective interpretation by the prosecution,almost spiteful,and destroying a mans life in the process.