Do you guys promote offers for companies that have their phone number listed on the home page? I am not sure about this, because what is to stop from a lead to just call the number, and not fill out the lead?
dealing with this is going to vary heavily by merchant. If you are dealing with linkshare/cj merchants, a lot of them have a script that puts a unique promo code at the bottom of the website. Then when someone calls the phone operators are trained to ask for that code which credits the affiliate with the sale. You are really going to have to check it out merchant by merchant though to get a definitive answer to your situation.