Unplug the charger

 

Are you trying to toggle the fast charging option to off while your phone is plugged into its charger? If so try disabling that setting while your phone is not plugged in.

Or if you have one of those funky battery management apps installed (those that 'claim' to be improve battery life and other miracles), try uninstalling it. Or start your phone up in its Safe Mode and see if that option can be toggled off/on again.
You could also just not use a fast charging power adapter and use a conventional one (typically rated at 5 volt/2 amp (or older ones at 1 amp) but don't forget to factor the increased charging times when you're using lesser current chargers. You could also plug into a computer or laptop USB port (use a ver. 3.x USB port, older ver. 2.x ports will only put out 500 mA).

 

Safe mode:
https://www.hardreset.info/devices/samsung/samsung-galaxy-a50s/safe-mode/


Just using a non-fast charging adapter might be a more prudent measure. A viable, generic 5v/2A adapter can be found in countless retail stores and online sites, and at a low-cost. An example being:
https://www.newegg.com/p/359-011Z-0...hone_power adapter-_-9SIAF9U6NJ5686-_-Product