Hello,
your dial plan for UK/Au should be like
exten => _844NXXXXXXXX,1,AGI(
agi://127.0.0.1:4577/call_log)
exten => _844NXXXXXXXX,n,Dial(${TRUNKAPN}/011${EXTEN:1},50,o)
exten => _844NXXXXXXXX,n,Hangup
exten => _861NXXXXXXXX,1,AGI(
agi://127.0.0.1:4577/call_log)
exten => _861NXXXXXXXX,n,Dial(${TRUNKAPN}/011${EXTEN:1},50,o)
exten => _861NXXXXXXXX,n,Hangup.
Then, you must go to Vicidial-->Campaigns->Campaign Details->3-Way Call Dial Prefix and put the prefix "8"
You must ask the carrier if the need that you send the 011, because most of the carriers does not request it, if they dont request it, remove it from the dial plan.
Also, you can have both dial plan together, but less secure this way:
exten => _8NNNXXXXXXXX,1,AGI(
agi://127.0.0.1:4577/call_log)
exten => _8NNNXXXXXXXX,n,Dial(${TRUNKAPN}/011${EXTEN:1},50,o)
exten => _8NNNXXXXXXXX,n,Hangup.