Ah so this might what's happening to me. Are you hearing some music when trying to call the Sonic number then it just ends after a few seconds?
I can't make a call to my sonic number through my Sprint/Tmobile but I can vice versa.
Yep, that is exactly what I’m experiencing. Still on hold with T-Mobile
Edit: 11:20PM As I predicted, T-Mobile is trying to punt this back to Sonic... "We can highly suggest that we can contact the Sonic for they able to check the home number line ending in XXXX to check of there's any blocking for your T-Mobile lines"
“Got it! Let me check here some other options why is that happens to your home number. Just to set proper expectation, since the line ending in XXXX is not under on the T-Mobile account we have limited access to perform a basic troubleshooting on it. Our system advise us to contact the service provider for the line ending in XXXX to perform a troubleshoot for your home number.
However, since you got here I will still check for other options here for how we can help you with your XXXX home number.”
Edit: 12:05AM Just got off the phone with their "engineering" team, and they weren't able to diagnose it either. The 10 second tune that plays is "I'm Still Here" by Macroform