Need help calling outside Asterisk from an inboud call

I am trying to allow users to zero out to an operator which is an outside number. I am getting a SIP 408 back…It seems to dial the extension, but when the other side answers, it drops the call. I can hear the first part of the person on the other side. Below is the console messages:

– Executing Dial(“SIP/”, “SIP/|99|r”) in new stack
– Called
– SIP/ is making progress passing it to SIP/
– SIP/ answered SIP/
– Attempting native bridge of SIP/ and SIP/
– Got SIP response 408 “Request Timeout” back from

My extension.conf has the following entry?

exten => 0,1,Wait(1)
exten => 0,2,BackGround(pls-wait-connect-call)
exten => 0,3,Dial(SIP/,99,r)
exten => 0,4,Hangup

Any Help would be appreciated. As a side note, my supplier is seeing the call and see it release.

can you make a “regular” or “direct” call to that sip address? by that i mean can you goto the cli and type the command dial “XXXXXXXXX@context”