Prepaid SIM M package still issues

I would like to notify that the issue I read online where the Prepaid SIM cannot connect to the server because of insufficient balance even though the SIM was purchased making the full payment for 6.5GB data , has affected myself as well. I bought the SIM card two weeks ago and for about 3 days I could not connect to internet. AS no one speaks English nor in the stores nor online, I found a friend to help me and we found that the balance on the SIM was 8Euro instead of 15Euro. We went to the O2 store in person, and the clerk verified that the balance was not enough to use the data. The SIM card was purchased in a Marktkauf store. The clerk said it is not O2 responsibility to solve the issue but it is of the Marktkauf store, which is ridiculous given the fact that the cards are O2 cards. So, as I was in need of a German number I made another 15 euro payment. This, in my country qualifies as FRAUD. As I was not able to reach anyone by phone or email or chat that can speak English I would like to know if my case (2022 September case, these SIM are still around) can be solved by someone at O2. In the case of no answer I will consider to send the case to the German consumer association, for the protection of consumers rights. Thanks for understanding

Edit o2_Bianca: Moved from Prepaid to English o2 Community Mobile