Question : Avaya IP Office 401 - problem with 5402 DS phone

Can someone please help me with this?
OfficeA extn 841 has no dial tone, they can make calls on it but cant hear the caller on the other end. I tested this and when they rang me from extn 841  the call went through OK and I could hear them fine but they couldnt hear me at all.
The OfficeA Avaya IP Office unit is IP 401 NG 3.0(40) and extn 841 phone is an Avaya 5402 DS? I think?
I have checked the manager configuration comparing extn 840 (which works OK) vs 841 and cant see anything wrong/different there?
What could cause this problem? I was about to try swapping the 5402 phone handset with a known good one and/or checking the cabling in the office?
Thanks for your help
-Dee

Answer : Avaya IP Office 401 - problem with 5402 DS phone

This sounds like a problem with the speaker on the handset.  Can you hear dialtone on the speakerphone?  I would certainly try to swap the phone for a known working one.