Sounds to me to be a set restriction done by the console. Have you tried the following on the console:
-Press Function
-Press Guest Room (F5)
-Dial the ext of the set not working
-Ristric O/G (F5) this stands for restriction outgoing and each time it is pressed it toggles through internal only, Local (plus internal), and Long Distance (plus local and internal)
-Press Exit
Does that do the trick?
-Daniel
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