iPhone XR earpiece speaker problem

I have purchased an iPhone XR in January and it was brand new.

Three days ago I started noticing that my top speaker's quality had decreased , and today the top earpiece speaker sounds like it's covered with a finger. It's very quiet and muffled, the bass sounds are also distorted.

I checked all the responses to this, and nothing worked, and I hadn't done any damage to it, nor water neither any dropping.

Does anyone have any idea?