Complain about TV repairs

Hi, I was very disappointed today at fair price in bochum, I bought a TV at fair price from bochum, it was a lay bye, I finished paying for the TV in November 2019 so they did not give me a receipt to show that I have finished paying. In July the TV that I bought just stop working,i called fair price for repairs and they told me that the technician are not working and they will let me know as soon as they start working. I called again on Friday the 21 of August 2020 and they said we can bring the TV because the technicians have started working. We took the TV there with the lay bye receipt, and they said they wanted the last receipt of laybye to show that we have finished paying which they did not give us. Today I went to fair price in bochum, I was helped by the guy called Ben which was very rude to me and my sister and he was forcing us to agree that they gave us the receipt which they didn't and he said they won't fix the TV without the receipt. I called head office to enquire about the matter and I spoke to Mohamed and he told me the same story and saying that they can't even go back to reprint the receipt, when I asked where do I go if I want to escalate the matter he dropped the phone. And they said the receipt that we gacmve them shows that we still owe 400 which makes me wonder how did they deliver the TV if it still had an outstanding amount

Maphuti/moba letlalo ***