Best way to monitor for issues with hosted VoIP and Skype issues.

Hello r/networking,
My company recently opened a smaller satellite office (20 users, mostly execs) and it had a bit of a rocky start with the network. We originally had an issue with our Fortigate firewall's SIP helper which we disabled and fixed issues with calls dropping etc.
The above incident unfortunately killed the faith of some of our users and they typically assume any static on a conference call is an issue with our network. I have noticed a legitimate trend albeit small of people reporting issues calling into our office or two another of our offices. Here is our setup:
-Skype for Business/Audio conferencing. (this is where a lot of meetings are hosted and issues are often reported)
-Hosted VoIP with OnSIP (people using their VoIP phones to dial into meetings frequently) -Hosted conference bridge lines through GlobalConference (some meetings are hosted here but not nearly as much as Skype due to no video capability)

  What I would like to do is monitor the network traffic involved closely to try and understand when and where we might be having issues. I've previously done some packet loss tests between our network and the hosted VoIP servers and ensured there isn't anything causing EMI in our office for example. I also have our VoIP subnet and VLAN removed of any security policies that should cause problems. Are there any tools or guides to troubleshooting the traffic involved with VoIP? Since all of our services are hosted, I'm assuming there is a way I can look for packet loss or latency issues from user>server>user?
Essentially my goal is to do my due diligence in ensuring QoS. I'm not asking for anyone to hold my hand or give step by step instructions. Although I appreciate anyone pointing me in the right direction!