How to transfer the call : 2dial or t?

hi all
i have a problem with the transfer. if I call the number of the line fxo, i get the girl of a2billing who tells me a lot things BUT she don’t tell me to make up a number. I don’t have the possibility to type my code and after to call someone.
I want that if someone call the number of the line which i put in the fxo, the serveur asterisk tells me to put my code and after it tells me my credit, etc …
any ideas to how to do this ???
thanks a lot in advance .