Hi AbhijeetDas211969,
Thank you for reaching Microsoft Community.
Please contact our PC Accessories support team for assistance in getting your Microsoft Wireless Desktop 850 replaced. To contact them, kindly follow the steps below:
- Please go to help.microsoft.com
- Under Microsoft Support, please click "Contact a Microsoft Support agent".
- Are you able to sign in to your Microsoft account? Select "Yes".
- Click "sign in" then sign in to your Microsoft Account.
- After that, you will be asked to Select your product. Click drop down and select "Microsoft Accessories" then click "Next".
- Select "Call me back" then enter your phone number.
Hope this helps.