It is not possible to rename a payment device once it's been created. The only option is to create a whole new payment device with a new name. However please be aware of 2 conditions:
1. Order numbers on the device will start from #1
2. Any open orders will not be carried over to the new name created
Note: To create a new name, you would need to delete and reinstall SalesVu iPad POS software. Select 'Dont want to recover' to create a new payment device and name after you've logged in