Samsung A2 core

I bought a Samsung A2 core for my son last year February 2021. April 2021 had to be taken for repairs and I was not charged since it is not my fault. On the 10th January 2022 same problem occured and took it to the store I bought it from. I was called and told that I will be charged because it is negligence from my side. Phone on flight mode is a neglicence from my side? How come to I have to pay for a phone that is still on warranty? A phone that has a problem with flight mode that I was not told about when buying. I refuse to pay for something that I did not damage. Please assist.

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