Authentication Of Customers

Hi there :wink:
Best wishes for anyone in this forum :wink:.
I want to implement something like authentication on Asterisk incoming calls.
Imagine that we have an operator in our system with an extension number : 141
and we have three customers :
Customer 1 : customer number : 19381
Customer 2 : customer number : 19382
Customer 3 : customer number : 19383

each customer calls our system, and this workflow will be started :
1- Customer 1, calls the system
2- an agent says : Hi, please enter your customer number.
3- Customer dials his/her customer number : 19381
4- system checks the dialed number, if it exists in existing customer numbers .
4-1 : if yes : customer can contact the operator
4-2 : if no : customer will be rejected.

NOTICE : all of the customer numbers are dynamic defined,
i mean for example we have a web based user interface, that writes customer numbers
in a single file.
an all of the checking in asterisk is file-based -> asterisk checks the dialed number with the numbers in that file.

and so on !
please help me.
i really have trouble !

Best wishes.