I had this problem on two Tracfones with different phone numbers. To try to keep their identity straight I attached a small strip of tape with each phone number along the top of the phones screen. Later when I tried to dial a number I got the immediate black screen thing. I never thought about the proximity sensor “seeing” this little strip of tape. I spent hours on the phone with Tracfone tech support without resolving the problem. I checked online, saw this forum and this thread and the lightbulb lit up. I removed the tape and PROBLEM FIXED!
Thank you so much!!