Generally, if an app becomes frozen, and/or your device becomes unresponsive to your touch, or button presses, then a forced restart usually solves the problem.
Also, if your phone appears to be off, but won't turn on or charge, a force restart may solve this issue aswell.
To Perform a Force Restart:
Hold down BOTH the top Power Button AND the front round Home Button at the same time for 15 seconds.
You can let go when the Apple symbol appears, or after around 15 seconds, whichever is sooner.
If the Apple symbol does not appear, then please contact us, or purchase a Diagnostic for your device through our website.