Hi!
I would suggest splitting the test like this:
exten => 1235551212,n,GotoIf($["${REVERSAL_REJECT}"!="TRUE"]?post-reverse-charge)
exten => 1235551212,n,GotoIf($["${CHANNEL(reversecharge)}"="1"]?macro-hangupcall)
exten => 1235551212,n(post-reverse-charge),Noop(Post reverse charge check)
edit: This works (now) thanks to the input I received further down this thread... I have removed the double underscores in front of the REVERSAL_REJECT variable, those must not be there when the variable is retrieved, it must only be there when the variable is set.
Have a nice day!
Nick