How to restart frozen Sony Xperia SP handset with fixed battery

Friends, my old Sony Xperia SP is frozen, I can't find way to restart it because it comes with fixed non-removable battery. Now phone is all blank, not turning on or off. Since my phone's battery can't be removed, I don't know how to restart it. I tried holding down power button with volume up and also with volume down but nothing happens. I am sure its just simple problem can be fixed by restart and I dont' want it to take to service guy.

Any help ?

Guide on internet are showing how to reset like factory reset your phone but no guide for simple restart ..

There are two ways to do it, one is to keep pressing power + volume button , that will do a power cycle on phone. Other way is to open back panel and look for a pin hole just above battery, it generally says "RESET" or "RESTART" , press it briefly using a pin and it should restart your phone.

This button is generally in all Sony phone with fixed battery in order to help people to restart in case of frozen phone.