how to distinguish which user is to buy my product?

 

I am a automated trading providers, there are many products trading, usually will receive feedback tens of thousands of customers, but time is limited, I want only to provide technical support to paying customers, so you can save a lot of time, but I how to distinguish which user is to buy my product?

 
scuxia:

I am a automated trading providers, there are many products trading, usually will receive feedback tens of thousands of customers, but time is limited, I want only to provide technical support to paying customers, so you can save a lot of time, but I how to distinguish which user is to buy my product?

You should ask you customers to provide their payment ID to confirm their purchase. They can find it in their profile/Purchases section. You then can compare the ID with a corresponding payment ID in your account - these two IDs should be successive numbers. It's up to you keep the list of the customers actual. But you can ask them to become your "friends", so you'll get the list just on the site.