Incoming calls from non-US destination

I see a strange problem today. I had an incoming call from international destination. When I pick up the call, I hear dead air. I called back and they said, the phone keeps ringing. It doesn't even go to voicemail. This happened about 3-4 times.

I made some test calls with my cell phone, and everything seems to be fine. I even had a US call before this happened and call connected frine. I have created a ticket for this issue.

Tech support has responded to the ticket and mentioned this problem is fixed. Haven't been able to verify yet.