OnePlus is launching the OnePlus 3T sale this December 14 on Amazon India, but Amazon Prime members will be able to buy the device 2 days before the official launch. Amazon is hosting a Early Access sale with Amazon Prime members and the OnePlus 3T will be available for purchase on December 12, to all Amazon Prime users.
It is important to note that the purchase availability is not guaranteed though. The stock availability seems to be minimal, and not all Amazon Prime users will be able to buy the product. The ones with the fastest checkout flow will be able to get the smartphone.
If you miss the early access sale for whatever reason, you can always opt in for the open sale on December 14.
The Amazon Prime Early Access sale for the OnePlus 3T needs an email registration though. Go to the OnePlus 3T Amazon Prime Early Access sale page and sign in with your Amazon account, if you not logged in. You will be added to the sale mailer immediately. You are now eligible to buy the item on the December 12 Early Access sale.