Trunk lag and talk-over problems

I’m about at wits end trying to figure out a solution to phone lag or echo. I’m in an office with 12 users and continuously get complaints of ‘lag’ and ‘talk-over’ problems.

I’ve tried several different trunk providers and each seems to be the difference in my echo tests. Below is an example:

Those echo results are in seconds. Is this standard fair for VOIP and is something obviously wrong?

All of those figures are unacceptably high for round trip times.

I was hoping this was the case. The ‘test’ numbers are on a freepbx disto 12.0.1 setup locally using flowroute as the trunk. Suggestions on how to diagnose what the problem is? Primarily using Yealink T46G phones. Thanks!

Things I’ve tried:

Changing internet service provider
Changing network switch
Removing any firewalls
Changing trunks
Changing phone manufacturer (Yealink to Grandstream)
Installing PIAF

All changes yield similar results on those echo test numbers. If I’ve changed the networks, phones, servers, and the trunks what am I missing? I have to assume this is a universal issue. Would a FXO gateway to a local PSTN improve these echo issues?