Voice mail -> 0 (Mail box options) -> 4 manage temporay greeting -> 2(Erase Temporary getting)->System Responds (Your temporary greeting has been remove)
The problem is that callers still get the temporary greeting after the system states that it removes it.
Free PBX 2.7.0.6
Voicemail 2.7.0.1
This fixed bug, that was fixed in 1.6 branch, looks very similar: https://issues.asterisk.org/view.php?id=14949