I had a similar problem with claiming for the free earbuds that were offered when I bought my S20 ultra. I sent them a copy (photo) of my order from Carphone Warehouse along with a copy of the receipt email that was also emailed to me. There was a bit of back and forth in which I complained to them that as a long standing customer I was surprised, disappointed and saddened to be treated so shoddily by a company that I'd hitherto been a reliable and happy customer of etc. This along with my indication to them that I would now put my plans of buying other goods from them on hold and would be warning all my family, friends and associates about the dismal experience I'd had with what I'd previously believed to be an honourable company etc.... Good luck.
