Calling non-human numbers

I’m running with POLYCOM 501 phones. The only Codecs I can dial with are ulaw and alaw. When dialing most numbers, I have no problems. The ones that give me fits are non-human numbers
AT&T conference - 877-336-1829
Smartinvestor 401K - 800-777-4015

When I call these numbers (ZAP TDM401P), I get the answer on the other end, but Asterisk does not bridge and the call hangs up at the end of the Dial duration. Any thoughts?

Answer before Dial will keep the line open, but a bridge never occurs.