2. If he refuses to name the boss, or deceives you that he is in charge, you can say some payment methods to see if he can decide. He may put the price first. That's all, but you should also know the process of payment. If he hasn't decided, he won't dare to decide.
If you think their sincerity is shallow, you can say that you want the samples to be recognized. If everything is stable, invite them to visit your factory or something, and then invite them back.
4. If starting a business is mostly a collision of small opportunities, then work hard. It is normal to change the telephone quotation, but it is more formal to mail the quotation.
Summary of personal documentary: I have dealt with such guests, which is very common. We can think of other ways. In short, adhere to clear, definite and principled business.