Connecting Elastix to a voip provider like voipstunt is not complicated, but it is important to put all the right parameters, particularly, the registration string.
First, lets create a SIP trunk, define a name, an outbound caller ID and a max number of channels
Then fill the Trunk Name and peer details as in
And finally, set the Register String as in:
Submit changes and Apply
Finally, add your trunk in an outbound route