Was why I bailed on Sprint years ago.
For very little, if your S6 has GSM you can test drive Tmobile or Att with a SIM card. I have one and ordered the other noted by CNET's Cheapskate at https://www.cnet.com/how-to/how-to-get-a-free-data-plan-for-your-tablet/
My Freedompop SIM is in my backup phone and I ordered up the other SIM noted by Rick.
I have a samsung galaxy s6 sprint phone. About 30% of the time when someone calls me it rings on their side but not on my side. My phone does not even show a call from them in the log. They can leave a voicemail and i do receive that. I have been troubleahooting this for months now with sprint with no resolution yet. Doea anyone have any ideas? I am trying to figure out if it is the phone or the service.