I can’t hear callers on my iphone x

Try to turn up the volume using the upper vol button during a live call which is the only time it can be adjusted.

If it still is too quiet click here

If you can't hear any sound or hear distorted sound from your iPhone, iPad or iPod touch speaker – Apple Support (UK)

It may b=need a repair in the end.

"...I didn't . I hit the button by mistake. my bad..."

Ok no problem.

The battery is fine and in any case the battery and the iOS version is not relevant. Either the volume will adjust, or the phone hardware is broken .

Read this

How do the various iPhone volume controls… - Apple Community

then

Force restart iPhone – Apple Support (UK)

If no better you should arrange a repair 

iPhone Service & Repair - Apple Support

Or

 Contact - Official Apple Support

Anything other than Screen or Battery may be a replacement phone and the price is in the article under "Other damage"

See also:  Get your iPhone, iPad, or iPod touch ready for service - Apple Support

karen ~ Does your iPhone X still have its original battery?

And what's the Maximum Capacity % here?...

Settings > Battery > Battery Health

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How on earth did that solve your problem????

karen238 wrote: "88%"

And, again, does your iPhone X still have its original battery?

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karen ~ Thanks, the battery appears to be ok. What version of iOS is your iPhone X running?...

Settings > General > About > Software Version

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You're welcome, good luck.