I bought an asus labtop in 2022 November and now the battery is not working

I bought an asus labtop in 2022 November and now the battery is not working. My laptop doesn't work if the charger is not plugged on.i went to the store to inform them and there was a nice guy there who believed that there is a fault with the battery as the device is with 24 months. However they couldn't assist me because I lost the slip but I have the transaction date. In cases like this what must I do?