Usually when people complain they cant be heard it is usually due to room noise levels or too many people trying to talk at the same time. I would investigate this to make a determination if there is any problem. Some of the telephone sets are better set to handle speakerphone conference calls and some areas are better set to hold speakerphone conference calls. If you are trying to conduct an speakerphone conference call in a average or larger conference room with multiple people there and even more connected via conferencing then I would greatly suggest a full-duplex conference unit that is designed for the purpose.

A Toshiba desk telephone that is a speakerphone is used primarily to conduct a hands free call but not a conference room scenario type call.

Its best to check these reported problems out yourself first and determine all factors.