Thank you, acejavelin and TE, for your replies.
... how do i tell what trunks do we have?
* from the "MiVoice Office 250 System ADministration & Diagnostics" program > System status (tab) > Bay/Module Status (section), there are 3 bays: Bay 1 - Digital Desktop Module (i'm pretty sure those are digital line); Bay 3 - Loop Start Module (i'm pretty sure those are analog lines); Bay 4 - Dual T1/E1/PRI Module (these are the ports we use for our IP phones... but what trunk type are they?)
* from the "MiVoice Office 250 System ADministration & Diagnostics" program > System information (tab) > System Information (section) > Platform (sub section) > click Hardware ID -> License Information > General > Software license features, there the count for SIP Trunks: is 0
* when I go to DB Programming > MiVoice Office 250 > System > Trunk-Related Information > SIP Gateways > 1 (the only option) > SIP Trunks, it's totally blank there.
Base on above, can you tell what trunk types we are connecting the IP phones to? (Or, is there other place I can look for a definitive answer?)
The issue is not with users on headsets, but the IP phone handsets and speakers.
(no wonder... proprietary trainings...)