[Q] telephone hangs topic

a good day to all of you!

i purchased a sony xperia E3 just about a couple of months ago. initially everything was fine.

suddenly, without any warning, the cellphone has started acting up since the past 20-odd days. i would rate myself at about 2.5 on a 1-10 geek scale, and shall be grateful to receive simple instructions to follow :

this is what happens:
- when i call a number the screen bricks; no possibility of stopping the call, or proceeding with the call, or returning to the contact list - nothing ever happens
- the other applications though of the cellphone are accessible without a hitch - the phone mechanism alone stays on the blink

this is what i tried :
- i tried twice to restart the cellphone. result : disaster. The machine simply hanged, with nothing but the eternal, never-ending sequence of rectangles that indicate that the machine is trying something
- i reinstalled the operating system twice, but with no success

i shall truly be grateful for suggestions, as i'm at the end of my tether