Customer has a 128 and bought a Polycom analog wireless conference phone , I got her set up how to make 3 way calls , but she wants to have 3 external callers in the conference and the supplier told her she can , I have told them that 3 including themselves is the max If anyone can confirm or correct me please do so. tks.

You can have more if it's a real "Conference Call" from the telco. Pricey though.

U-TEL-US,
You are 100% correct. Only 3 including originator.