.call file returns call completes but phone does not ring

My goal is dialing an external number via a .call file to play a recording, and I am getting the message

pbx_spool.c463 attempt_thread: Call completed to SIP/mynumber@atlanta2.voip.ms

voip.ms being my SIP trunking provider, however my phone never rings.

This is the callfile I am using:

Channel: SIP/mynumber@atlanta2.voip.ms 
MaxRetries: 1
Context: voicebroadcast
Extension: 777

added this into extensions.conf

[voicebroadcast]
exten => 777,1,Answer()
exten => 777,n,Wait(1)
exten => 777,n,Playback(hello-world)
exten => 777,n,Wait(1)
exten => 777,n,Hangup()

I am a bit confused on the Channel variable within callfiles so I am not sure if the error is relating to that or something else. I did register my Asterisk server using the login provided by my SIP trunking provider and when I do “sip show registry” It is showing there as well.
I am still fairly new to Asterisk so bare with me if this question is a bit redundant.
Any information will help! Thank you.

can you try enable sip debug so we can see what the provider is doing
they may be answering you call an play a “there was an error”

https://wiki.asterisk.org/wiki/display/AST/Using+Callfiles+and+Local+Channels

also please start using same in the dialplan

[voicebroadcast]
exten => 777,1,Answer(1000) ;milliseconds
same => n,Playback(hello-world)
same => n,Hangup()

Is atlanta2.voip.ms the name of a section in your sip.conf file? If not, you will not be sending any of the authentication data that would normally be sent.

Note that chan_sip is no longer supported.