Microphone, speaker not working. Please read description.

I received this phone 3 days ago after buying refurbished from a small kansas city business off ebay, where they said it should be in full functional order, other than cosmetics which are very slight. everything is great but, when i first booted up into the phone and finished setting up, the speaker started crackling for some reason, i'm not sure why. i tested a youtube video, it played but pretty quietly and then the crackling consisted for a little bit afterwards until falling to a complete silence, where i am right now. after updating, factory resetting, restarting, making sure everything was turned up properly, nothing. and then it got worse when i realized my microphone was not working as well, and it would crash an app (i.e instagram) whenever i tried sending a voice message. even bluetooth headphones don't play any audio but i'm still going to try type c wired earbuds when they come in. i'm convinced it's a software issue but even if it is, it seems irreparable to my knowledge. if anyone has had this issue and/or knows a fix, please let me know because i'd really like to fix it myself before just sending it back.