No busy signal / endless silence

We’ve used with Asterisk for about 2 weeks now. A user noticed that when calling a certain number we got indefinite silence. Calling from my cell phone the number is busy. I found some other “always busy” test numbers and can duplicate the issue. That test number is 6193640003. My desk phone stays connected indefinitely. (I let it sit 67 minutes while I went to lunch). X-Lite going directly to and bypassing Asterisk gives me busy within 10 seconds. I checked my asterisk log and about 10 seconds after the call connects, this appears in the log (but no busy signal)

app_dial.c: – SIP/ requested media update control 26, passing it to SIP/303-000047a4
app_dial.c: – SIP/ answered SIP/303-000047a4

It looks like its trying to give me the busy signal I hear in the softphone but I continue to get silence. told me to seek professional Asterisk help since the softphone worked fine.

Anyone got any ideas?

what you are running and what your trunk definitions look like.