What mens won't do to call girls those days
A2Billing is not designed for this purpose, but I m sure you could use it to ease your task a lot.
There is a nice callback system that you could use.
If we suppose that your customer have an account on a2billing when clicking on the picture and entering his phonenumber, your website will need to call an API to outbound the call. I will advice you to check the code here webservice/api_spool_callback.php, this code might need a review.
Then you will also need to create a ratecards with the phone number of the girls and the amount you would like to charge for the call.
Cheers,
/Areski