I don't know this handset, but generally pressing and holding the power key until it asks whether you want to shut down or reboot does it.
If it's not responding to that, either remove the battery (if it has a removable battery) or just press and hold the power key until it shuts down. After that you can try restarting, and hopefully it will be OK (I say "hopefully" because if you have to do either of these then something was not right).
This site uses cookies to help personalise content, tailor your experience and to keep you logged in if you register.
By continuing to use this site, you are consenting to our use of cookies.