I am using Idev->Onestepcheckout extension. "Enable AJAX save billing" option is made yes from admin panel.
Now my problem is when I click on saved addresses and check chrome's network tab then I can see a action being hit i.e. save_billing. This action has the code for submitting the selected address to database.
Now If I select add new address option then I get a form where I can fill new address. This form is now submitted at the last after all the options are selected such as payment_method and shipping_method. But I could not locate the code how this form's data is submitted to database. My form action is "https://example.com/onestepcheckout/" . I checked index action of index controller in onestepcheckout module but I could not find any code there which is responsible for saving the above data to database. Anyone could help me in finding how the form data is saved.