No Assistance none whatsoever

I purchased an iPhone 8 Gold 256GB 29/07/2024 online . Device was working well until yesterday when callers started to complain about not hearing me , I tested the microphone with memo app sounded very bad , the sound was distorted till now . Tried Istore lines of communication still no response , its been nearly 2 hours now on a chat waiting for someone to help me . Sent an email no response unable to call as the phone is faulty . Tell me what should be done now ?