Callers comlaining about low volume

Our office accepts incoming calls using a SIP provider. All employees use softphones - I’ve tried both SIP and IAX soft phones. We can hear callers OK but they often complain that they can barely hear us. I have the mic gain on the PCs all the way up.

Can anyone suggest a solution?

are you all using the same mics ? perhaps you try something different and of good quality. and use whatever software you have installed to set the mic gain, most of the softphones have access to some kind of wizard.

have you mentioned it to your provider ? they might have your outgoing gains set too low.