iPhone battery won’t charge all the time

Are you referring to an iPhone here? If so, check out this support article from Apple with troubleshooting tips:

If your iPhone or iPod touch won't charge - Apple Support

If problems still persist, you might need to contact Apple to see if they can provide more support.

Take or send it in for warranty repair

https://support.apple.com/iphone/repair/service

Anything other than Screen or Battery may be a replacement phone and the price is in the article.

You can see additional service information within the following article:

Prepare your iPhone for packing and shipping