Pandora app running in the background

Since updating to iOS 11.3, I've noticed major battery drain on my iPhone 7. A big chunk of it (which is new since the iOS update) is Netflix, which I watch when on the treadmill at the gym for about 45 mins each day. Before the update a few weeks ago, no problems...I'd watch Netflix and it would use about 8% of my battery charge. Since the update it's draining my battery by almost 50%! Battery Health indicates Peak Performance Capability, though max capacity reads 89%.

So now I swipe to close the Netflix app after using it, but have noticed that the battery keeps draining. When I check the list of apps under Battery Usage, I notice Pandora is listed with background activity. Today it says it's been running 31 mins in the background. I can't even remember the last time I actually opened the app, but it hasn't been in many weeks. How is it running in the background? I have Settings: General: Background App Refresh OFF on my iPhone, so I assumed that would prevent apps like Pandora from running in the background (especially when I don't even open them), but apparently not. When I checked the Pandora app settings, Background App Refresh was faded out, assumedly due to my having it turned off entirely on my phone, but it did show that the selector was "on" for whenever I might have Background App Refresh activated. So I briefly turned on Background App Refresh in Settings: General for my phone, went back to Pandora's app settings to turn off the Background App Refresh for that app specifically, and then turned back off the Background App Refresh for my entire phone. It's just a hunch, but I'm hoping it will prevent Pandora from insidiously operating in the background when I haven't even opened it. If it continues, I think I'll just delete the app, since I don't use it all that often anyway.

Any ideas as to why/how this is happening with Pandora? And any thoughts as to why Netflix is suddenly using up so much more battery life?