[Android Central Question]

All forum comments imply that I can do anything with the phone, but the pop-up message stops me from doing anything, I can't even switch off the phone, not to mention getting into settings etc.

[Rukbat]

To switch it off, you have to be fast - tap OK, then hold the power button. Eventually you'll get the "power off" menu.

Then try turning it on again. Sometimes a system app (and com.android.phone is a system app) will "go crazy", but restarting the phone will fix it.

If not, turn it off again, then boot into download mode. You'll have to reflash the ROM. (I'd suggest connecting it to your computer first and saving everything you can get at - flashing a ROM wipes the phone - all your music, pictures, videos, installed apps, etc.) We'd have to know which phone you have to give you a link to instructions for flashing it, but you should be able to find them by googling flashing <and the make and model of your phone - without the brackets>. Or go to XDA Forums and see if someone has posted instructions. (If it's a common phone someone has. If not, someone may have.)