Poor call quality.

Hi,

I am sujin, I have purchased an iPhone Xs 64 gb a couple of weeks before. I am facing call quality issue during my phone call, the caller from other side not able to hear my voice clearly (muffled) but if I use the speaker phone option then i am not finding this issue, I am facing this only if I use the earpiece to talk. I have removed the case and switched off the noise cancellation option too, I have even formatted the phone to the factory setting and still facing the same. Feel like being cheated after paying a premium price. Need apple to resolve this issue immediately.