Software malfunction since update

There are a number of things that can cause the screen not to come back on when on a call. Are you using a headset for the call, or have you had the iPhone up to your ear? The screen is supposed to go dark when you have the phone up to your ear, but is supposed to light back up when you remove it. It does this by way of a proximity sensor near the earpiece. Some screen protectors and phone cases can obstruct that proximity sensor and it will not work well. I've seen a couple of people make comments about Messages behaving this way, but no further information provided. Since you have already turned the phone off and back on again, let's try the next step. That is a force restart of the iPhone. See the instructions here, Force restart iPhone - Apple Support

What kind of software malfunctions? This is a user to user support forum and Apple does not participate here. You need to type out a question describing your problem and any troubleshooting steps you have taken to fix it, and wait for one of the volunteer users to read it and one to answer it.

Read this, Writing an effective Apple Support question.

You're welcome. There is a proximity sensor that handles the screen going off and on when putting the phone against your ear. A crack in the screen could, and sounds like it did, interfere with the sensor light getting through correctly. Imagine looking through a cracked glass or window at how it distorts your vision, and it would scatter the infrared light from the iPhone sensor. Glad you got it working.