Hi CFW-APE,
Thanks for participating in the Apple Support Communities.
It seems like the volume up button may not be working on your iPhone. If you can increase the volume with the slider in Settings but not with the button on the side of the phone, try the following steps from Get help with buttons and switches on your iPhone, iPad, or iPod touch.
If any of these buttons or switches aren't working, follow these steps. Test after each step:
- Unlock your device. Some buttons don't work from the Lock screen.
- Check for debris or dirt around the button or switch and clean it with a soft cloth.
- Remove all protective films and cases that might interfere with the button or switch.
If the button or switch still isn't working, if it works intermittently, or if it's damaged, contact Apple Support to set up service.
You may also want to try restoring the iPhone before contacting Apple Support. See Use iTunes to restore your iPhone, iPad, or iPod to factory settings. Set up your device as new (in Step 5) and test the volume button with the iPhone in factory condition after setup completes.
All the best.