Head to POS Devices
Hover over 'Apps' and navigate to 'Point of Sale' and then select 'Devices' from the menu options.
It's important to note that you should only deallocate a device if it is not currently in use. If someone is using the device, it will prevent them from finishing any transactions or processes they are actioning and kick them off
Scroll down to the device you want to deallocate, under the Allocated column it will let you know who the device is in use by
Click the more button and select 'Deallocate'
Re-assign the POS device
Once the device has been deallocated, you can then reload your POS page and assign the device again