Samsung — Purchase of Brand New Phone

I had purchased a Samsung A 71 from Global Access in Inidra Nagar Bangalore on 26/11/2020 (Dusshera). From the first day itself, the battery started draining out. And when I complained the same to the Samsung Service center more than once, they say to leave the phone with them for checking.
I have sent several emails to support.[protected]@samsung.com.
And in one of the emails which they (samsung) have replied is that I hand over the phone to the service center and that they would replace the parts.
Now why does a brand new phone need replacement of parts withing 15 days of purchase, nobody is able to explain. And if it needs replacement, means it is a defective piece, which the people in the service center are not willing to accept and they keep saying leave the phone for one day and we will check and revert to you.
Now what is the guarantee that if I leave the phone with the service center, they will neither replace the parts nor repair the same.
If they do, means the phone is a defective piece.
And another thing is that the person in the service center says that if any parts are replaced or if the phone is repaired, it will show in the system, What if they don't enter the details in the system, and then make the phone and say everything's ok.
I saw the trust of Samsung by purchasing a phone for 30k. I am not interested in trusting them again.
And I have asked for either a new phone, or my money back or a credit note.
They are not willing to give either of the above.
Therefore I request you to please look into the matter and grant justice by intimating Samsung to either give me a new phone, (the same Samsung A 71) or my refund back or a credit note.