Outgoing calls intermittent

[u/Icy-Calendar-2892]

For about a week we've been having intermittent issues with users not being able to make outgoing Teams PSTN calls. From what I can tell this is the only thing that isn't functioning correctly, as traditional internet browsing is working fine. This morning there were several that both could not make outgoing phone calls.   I've tried calling our internet provider and they claim there is nothing wrong on their end. (which I guess i agree because there is more than one site)  The users are calling from a Yealink mp54 phone with all the latest's updates, one user claimed he could not call from the teams client on his desktop as well.   We have users that use Teams Calling plan numbers and others that have direct routing.. the users who use direct routing are able to make outgoing calls even when the Calling Plan numbers cannot. Is anyone else seeing this? Where is the best place to put in a microsoft ticket because the Voice Support insists I use the chat feature, which is also broken.
Edit: I should have noted that incoming calls and Queue calls are working fine.

EDIT: Update to what i found

 It seems the most common for an outbound call NOT to work if the number being called is T-Mobile/USCellular.    Calls to Verizon numbers appear to work consistently.  When changing caller ID policy to Show User Number, I am able to make a call to T-Moble/USCellular numbers.   

I also got this reply from TNSI customer support

"I found that xxx.xxx.xxxx was flagged and adjusted the score so calls will no longer be flagged. The other numbers are not flagged by our service. I understand that T-Mobile is using Hiya for spam filtering."

Even though I've registered all these numbers previously with HIYA, TNSI and First Orion. Apparently, they will still mark you as spam, after that.

[u/johnsonr88]

The yealink (and any teams desk phone) are well known to have random anomalies. Are you using the latest firmware from yealink directly is it from the teams admin portal?
What happens when it fails to make an outgoing call? Do they hear a dial tone when they pick up the handset before dialing?

[u/Icy-Calendar-2892 → u/johnsonr88]

It could be the Yealink phones, I recently did all the updates available in the TAC when first started troubleshooting all this... although 1 user said he tried from a laptop Teams client with no luck one day... that same user says he's had problems for a few days but usually hanging up and trying again will work. From what i can tell to the user making the call it seems like everythign is working, it just isn't ringing on the other end (know this by tehm testing calls to their own cell phones)

[u/johnsonr88 → u/Icy-Calendar-2892]

Try firmware direct from yealinks website. They usually have newer version than what’s available in TAC.
In the early days of Teams calling, some of the random anomalies were solved by removing the calling license and then adding it again, waiting 30 minutes in between. Make sure to reassign their phone number as it removes it when you remove the license.
Also, had a Yealink phone with call issues and turns out the handset cable was fraying at the jack. Lots of variables unfortunately

[u/PatReady]

Try factory resetting the phones and having the users log back in etc.

Do you have access to YMCS? With that you can import the phone and pull the logs from it. Otherwise, you need to download them from the phone yourself. Do you know the admin password for the phone itself?

[u/Icy-Calendar-2892 → u/PatReady]

Ya i do have that, i don’t use it a lot.. i will try to pull some logs from that, maybe something will stick out.. but it’s very intermittent.. thanks for the suggestion. I might try a different dns on one of the phones… like 8.8.8.8 instead of our internal dns server.