My battery is showing the charging indicator when plugged in but it’s not charging

As long as it is plugged in it will show the charging indicator, whether it is charging or not. It will stop charging in 3 situations:

1. At 100%
2. At 80% if you fast charged it; it does this to cool down. It will resume later ( 30 minutes or more) but charge at a much lower rate. It may take an additional hour to reach 100%
3. At 80% if you have enabled Optimized Battery Charging and you charge overnight; it will resume in time to reach 100% around the time you start using the phone (based on your average usage)

If the phone is in a hot environment it may stop charging at other times to cool off.

This symptom could also mean you are using a poor quality or defective charger or cable (if you are not charging wirelessly)

Try a force restart

Force restart an iPhone with Face ID

To force restart iPhone X, iPhone XS, iPhone XR, iPhone 11, iPhone 12, or iPhone 13, do the following:

Press and quickly release the volume up button, press and quickly release the volume down button, then press and hold the side button. When the Apple logo appears, release the button.

if this doesnt work try using a different charger-apple certified 20 watt will charge your phone fast.

It's not a "charging" indicator per se. The lightning bolt inside a battery indicates that it's connected to external power. It's always possible to have a really low output power supply, and using the iPhone while it's plugged in will mean that the charge level still goes down.

What are you using to charge it?