Caution, unsightly business!

Caution, unsightly business!
I bought a Samsung tablet from a campaign in summer 2017 that promised me a refund of 120 from Samsung (campaign "Urlaubskasse").
The device itself is OK, but I would like to warn you here at this point before participating in such cash-back campaigns from Samsung.
To do this, you have to upload the invoice etc. after purchase - as far as everything is good. However, there was then a request for a detail in which I should send a photo of the outer packaging of the device within a week - which of course is not necessarily possible during the holiday period if you do not have your outer packaging with you on vacation.
I take something as a deliberately chosen trick, so as a very ugly business practice not only from the processing company, but also from Samsung itself. Both refused to pay back with reference to the terms and conditions.