ok understand how you feel indeed as you been rejected to send back your device.
what is their stand point - I mean if that's because they said your devices are bought online? do you have valid invoice on this? (confirmation email/ payment detail etc)...

seems like there are one Nodic user also experiencing this before (the local Support centre said the user has no valid invoice as he bought his device online)... but later the user supplied them with all the emails/ payment transfer details... then they accepted it.

by the way, where is your country of residence? there may be some slightly difference in the way they handle the case... varies from country to country.