Include fax field in orders table

[TheFinnisher]

I would like to include the fax number in the orders table so that I could use it in my payment module.

 

How are the customers and orders tables connected?

 

I added a field named customers_fax in the orders table and this is my payment module:

 

tep_draw_hidden_field('x_Fax', $order->customer['fax']) .

 

but I can't get it to work...