Apple iPhone XS max - Face ID unlocking with multiple people

I have brought an apple iPhone xs max last year and this phone has a special feature face id unlock for mobile. On this phone I have set my face id to unlock the mobile and notes, WhatsApp, google pay etc for many personal data. Recently one of my friends took my mobile and was using it I was thinking he doesn't know my password and the face id doesn't unlock anyway. But its got unlocked by his face and even with some of the other people. Even the google pay, personal data apps like notes all the getting opened with multiple faces.
So I contacted the apple customer care and told them this issue. What they come to tell me is you should update the software so this problem will be fixed. I have done it and then again it remained the same. They told reset face id I did it and again they told reset mobile itself I have done factory data reset then it was fine. Again in * days, the same problem has come then they told me to take a video and send. I have done the video and sent them they again told reset face id and told me to send some analysis of mobile and tell me that the mobile is alright you will not face this problem again. But they have made me call come **'s of times waited for so much. Since today from * months my problem isn't solved?
I don't understand if we don't update software the face id unlocks? If we don't reset it unlocks. I have purchased it more than * lakh rupees and if I face these kinds of issues how will I feel my self inside and their response I have nowhere seen such bad response.
At least if my mobile is not under warranty I would leave it. It's under warranty only and they are not even caring? I don't know what else to do? Where to go? Apple people have given me case id number: ************.
If you can provide me with any attaching video files here I will attach the video of the iPhone which is getting unlocked by multiple people.