Use asterisk as client to act as a soft phone

Question

I have an account with vonage and I am able to make phone calls from my computer entering the following information into my soft phone (zoiper):

When entering that information (domain,usrename and password) into my soft phone settings I am able to make phone calls and also receive. At this point everything works great

Now my question is how can I make outbound calls from asterisk using that same information that I got from vonage? I would like my soft phone to connect to asterisk, then asterisk making the outbound call.

This is what I have tried:

This is how my sip.conf looks like:

[general]
   tcpenable=yes
   etc.....

 [SoftPhone1]
   secret=MySecretPassword
   context=MainContext
   type=friend
   disallow=all
   transport=udp,tcp
   etc...

 [vonage-test]
   type=peer
   host=sip-55623.accounts.vocalocity.com
   secret=*********
   username=VH283034
   disallow=all
   allow=ulaw
   transport=udp,tcp
   dtmfmode=auto
   insecure=invite

and on my extensions.conf

[general]
  static=yes
  etc...

[MainContext] ; this is the context where SoftPhone1 is registered
  exten => 100,1,NoOp(Testing to see if we can make outbound call) ; just write to the console
  same => n,Dial(SIP/3051234567@vonage-test) ; make phone call to 3051234567
  same => n,Hangup()


  etc...

when I dial extension 100 the call never goes to phone number 3051234567. Why?