I'm having the same problem. XXX-XXXX was rejected.... error message 503
yesterday my wife dialed a number and got a reject. I assumed she just misdialed so I used click2call and initiated the call for her.
today I dialed a 7 digit number and got a reject. I had been playing with my configuration earlier and thought maybe I didn't it back right, so I just dialed the call using 10 digits.
Later I dialed a 888 xxx xxxx number and got a reject, so I dialed it using a 1 and it went through.
Soon after I dialed a 7 digit number and got a reject. Hung up and immediately dialed it again as a 7 digit number and it went through fine.
It seems everything for me in intermittent as I always dial 7 digits and it doesn't happen every time.