3CX have recently increased their licence costs dramatically. The costs are based on simultaneous calls, but there doesn't seem to be a way to find your highest ever simultaneous call usage, so I wrote this.
Download your unfiltered call log (Reporting>Call Log>Export), put it in the same folder as the script and run the script
It will take a while
Output csv file should give you every second during the 90 days and how many simultaneous calls there were during that second (if there were more than 3 calls because otherwise the file would be biiiig. Change the number on line 35 if you want to change that.)
Is it slow and inefficient? You betcha!
Is it accurate? I hope so because I've just used it to halve our licence, which means I'm paying less than before the greedy sods increased it inflation forced them to reluctantly raise their prices.