Hello Everybody, now i start to know that people can refund paypal payment just by a note when he/she paid, say somebody will pay you 100us, then he/she send you a paypal payment, and it looks like normal, but he/she already put a note to the payment that he/she may ask money back someday. And then you make despatch the order right after paypal payment. Problem comes then, paypal could send you a ltter to refund the 100usd even 2 month later, now you lost control and even the delivery bill was cut because of long time idle.
Please do be very careful now, paypal payment is not good.