Hello I am Samuel and I can support you! What model device is it?
I am going to assume it is a newer Iphone?
If it is indeed a newer Iphone please hold down the power button and the home button for 20 seconds! That should do the trick!
Kindly rate my service 5 stars at the top of your question page if my answer helped so I am rewarded for my time; tips appreciated :)Otherwise please reply back if you need further assistance. Thank you, Samuel