Why does my cellphone still turn off after charging?

Hullo goodevening,

how long have you had the phone for? is it always on charge? when do you start charging it from? 10% or 70%.

could be a battery fault or physical problem if so then replacing it would be the easiest option.

other quick tests could be Battery Calibration:

• Let the battery drain completely until the phone shuts down.
• Charge it to 100% without interruptions, then restart the phone while it's still plugged in.

Reset the Phone:

Perform a factory reset (after backing up important data) to rule out software problems.

only do this if you have a backup but make it a last resort

Use apps like AccuBattery to check the battery's health. its not perfect but could work

goodluck