[Asterisk-Users] Individual SIP account how to make it Trunk

[Jolly M. Recto]

Hi,

i have diffirent provider example(3 single account in deltathree,  4 
account in  packet8 and so on) . How this possible to make the three  
individual sip account in deltathree act as trunk so that i cannot get a 
busy call. If line one fail goto line 2 then line 3 or another trunk 
line 1 then line 2 then line3....I read it in asterisk at home but the 
script i am copying is not working .

any help is very much appreciated..
TIA

//jollyr