iPhone 12 PM earpiece sound.

I can’t seem to figure this out and Google ain’t helping. My mom have an iPhone 12 pm and the problem is when you playing any sound as in YouTube, TikTok, and Apple Music.. it’s all coming out of the ear piece. It sounds so horrible when you turn the volume up. Even during a phone call. The earpiece seem like it’s very loud and muffled… like it’s trying to use the speaker as the earpiece like it’s normal. Idk what to do. Pls any help would be appreciated.