All four buttons on the lower part of the phone are not working. I was using the browser when the became unresponsive. I tried turning it off and on, taking out the battery and letting it sit for 5 min, turning it off and letting it sit for 5 min, and charging it. What can I do to fix this problem. I see in some posts people have said things about typing in a set of numbers into the dialer, but I would prefer to do something that isn't going to possibly cause more problems.