Hi Ahmed24, looking in the WebGUI the only way I can think to approach this question / absent a formal report or log in the system it seems?
(a) Manually test and see if users complain -> go into your SIP Trunk config page and in the 'options' area there is an option you may edit (I think, at least in the 3cx instance I just reviewed this is the case) -> called "Number of sim calls per trunk " which can designate at a SIP_TRUNK level how many concurrent calls the trunk supports. So for example if you are currently paying for an 8SC license and wonder about downgrade test to a 4SC - dial the setting here down to "4" and wait and see if end users complain about call throttle issues. If nobody notices and no complaints after a few days of peak-hours-use-activity, then this suggests you might be OK with a reduction in license count and nobody would notice. In contrast if there is lots of pain and suffering, you probably will have answered the question quickly, and you just dial up the throttle to the original number again (10? depends on your SIP trunk provider I believe) and 'carry on business as usual'.
(b) Alternately if you leave the web page open in your browser on your ~second screen of your computer for an ~hour during peak operating time:
https://YOUR_INSTANCE_NAME.3cx.com/#/office/dashboard/active-calls
and just visually keep an eye on - how many active calls are displayed in the queue during this peak time of day (ie, for example if you know the phones are most-busy based on staff discussion-feedback during the 9-10am slice of the morning?)
that could be a ~boring trivial way to try to validate/confirm what the call volumes are like.
(c) there might be possibly some 3rd party 'screen scraper' software you can install and configure to manually harvest the number of active calls off the dashboard web page / if you hit the page every minute and do string matching or something like that, but clearly this is a bit of a klunky approach.
not sure if this is helpful at all. If you find a path towards a workable solution maybe do reply back on the thread?
Tim