Microsoft normally offers Lumia promotions with new Windows Phones it sells, and its a bit hard to keep track of what’s on offer for what and where.
To consolidate all these offers and gifts into one app. Microsoft has released a Lumia Offers app that details all the offers currently available for your device.
Currently there are only two offers available for my 640 XL (Gameloft Switch and Windows Gift), but there may be more depending on your preferred device
Here’s the store description:
This application brings together the best Lumia Offers that are currently available to you
The app is only available for Windows Phone 8 devices and not on Windows 10 mobile devices at the moment.