call forwarding?

I use Google Voice for voice mail. I have always made sure this is set up by going into the call forwarding screens and then putting my google voice number in there. But today it is all grayed out. The background is - within the last several weeks, (and it was not immediately after installing any updates, so if there was an update installed, it occurred unbeknownst to me) my s7 Edge began experiencing EXTREME battery depletion. I had done everything I can to figure out what is causing this, but have yet to do so yet. Then, as of today, my text messaging started not working. So I installed a third party messaging app I have used in the past with no problems, and after a few messages in that app, the same sms/mms sending failures started happening with that app so I returned to the stock app. I did a cache wipe, uninstalled and reinstalled wifi networks... I shut down and restarted and phone and set phone to wifi preferred. WIth this setting, the call forwarding settings are greyed out. I turned voice to LTE and then cellular preferred; Then it would let me see the forwarding settings, however, ALL of my google voice forwarding settings are gone. And then when I clicked on the forwarding setting, I keep getting "ERROR - Sim card or network not available."  My text messages won't send, my phone is extremely hot in temp, battery is draining like 50% an hour; What is going on? Are google voice settings somethere else? What is going on with battery and messaging??

Thanks.