I suddenly got error messages one day that my battery was overheating, even though the phone didn't feel warm!?!?! The phone displays started getting intermittent, and so I tried fast-charging the S6, even while battery capacity was quickly dropping. While I was trying to export my updated Contacts to the Verizon Cloud and Google Drive, the S6 died. I haven't been able to recharge it since.
The Verizon tech who had set it up for me had promised that he would store the Contacts, photos, and text messages on the phone's internal memory (the SIM card?), but I don't know how to access those data now when the phone is dead.