Top earpiece and lower left speaker not functioning properly on iPhone X

Does anyone know if Apple will help with the issue of top earpiece and lower left speaker not functioning properly?

I recently purchased two preowned iPhone X’s From sprint PCs in in North America and bothe of them have earpiece issues like crackling. I had to order two replacement phone through sprint because of same issue last week. I’m beginning to wonder if all IPhone X’s were like this with such bad speaker problems. I had a lease for two iPhone8’s and decided not to pay the $33+ a month fee I was willing to pay the $22 for a phone but will probably be sending these back to sprint and just keeping the 8’s. I didn’t want to purchase the insurance this time around so I only have a 30day money back guarantee through sprint.

My question is will Apple stand behind their products even though opted not to purchase apple care or insurance through sprint?

[Re-Titled by Moderator]