provided by Star2Billing S.L.

our callback works fine for area code of Toronto
Like 416 647 work fine, however we got customers outside this area code, when they call our access number, it shows busy and then system calls them back, but after 12 sec system hangs on them (doesnt matter what number they enter), I have no idea why

[a2billing-callback]
exten => _X.,1,DeadAGI(a2billing.php|3|callback)
exten => _X.,n,Hangup

[a2billing-cid-callback]
exten => _X.,1,DeadAGI(a2billing.php|3|cid-callback|1)
;exten => _X.,1,Answer(10)
;exten => _X.,n,SayDigits(${EXTEN})
exten => _X.,n,Hangup

[a2billing-all-callback]
exten => _X.,1,DeadAGI(a2billing.php|3|all-callback)
exten => _X.,n,Hangup

any help would be appreciated

I haven't read your debug log, but I'd be willing to bet that you're not receiving DTMF on the callback leg.