Early February, 2018.

I have already done it through Galaxy App. You can also do it by going to offers section.

It is with me also on Note 8

On the pre booking mobile number one sms will be received containing code and link to Galaxy app after 2-3 weeks and then claim the charger through that link. I have enquired Samsung help and got this reply.

No problem as I use it. T8me doesn't matter.