Looks like i have also cought by the Banggood trap “Buy something and get NO gift”…. 
Send two suggestions for alternative solution, after the out of stock mail, they reply only that the primary item is on the way. Yes, i know, we are talking about the gift… 
After 3 days i got the Mail:
We regret to inform you that your order had been canceled since we have not received your reply after 3 days the email sent which asking you for exchange the item as the product out of stock.
Lying in the face of the customer is customer service that has plenty room for improvement…
