Apple India — i m complaining about iphone 11

I purchased my phone in nov 2019 but from feb 2020 it will automatically shutt down and i will give it to service center but they can refresh my phone and again get back to me after 1 week same problem occur and again i visit service center but again they told me there is no problem i also called customer care but they even don't know about the phone condition but that time i didn't call again but after 2 month again same problem occur but this time i can't reach to service care but this is worst service by apple customer care and service center plz suggest what can i do