provided by Star2Billing S.L.

here are a few ways to do it and not lose the DNID which is what drives the additional pricing

exten => 800number,1,GoTo(custom-callingcard-toll,${EXTEN},1)

dnid not lost because the goto is still 800number

[custom-callingcard-toll]
exten => _X., 1, deadagi(a2biling.php)

here is another approach i use when i have multiple toll free numbers but i want to keep it simple

exten => _X.,1,Set(CALLERID(DNID)=800800800)
exten => _X.,2,DeadAGI(a2billing.php|1)
exten => _X.,3,Hangup


i set the dnid to a defined number but notice i do not do any "goto" to cause the dnid to change

if i have to do a goto i use the exten variable so as not to lose the dnid

Yep.

Gue's suggestions should work. Here is a direct approach that I use quite often and it works like a charm.

You're not calling a2billing.php correctly; the agi-confX section is the 3rd parameter to DeadAGI. Here you have it as the 2nd parameter, which is meant to be the number dialed: ${EXTEN}

this is the instructions you executed. that is not what you said you have in your extensions.conf

The call is not taking the path you believe