I've been experiencing a very serious problem when receiving calls. When someone calls me, my phone will ring but the screen will not turn on. In some cases I can swipe the black screen where the answer bar should be and take the call (without knowing who the caller is, which is very annoying). Other times the phone seems to completely freeze and I can't even wake it with the lock button. In these cases I need to do a battery pull.
What is wrong with my phone? Do I need to get a replacement and will I have to pay full retail for the replacement?