I've come to this page almost every day for the past week and a half to see if more people are having the same issue. Super frustrating! I updated my phone about a week and a half ago. Have an iPhone 7. Update was working fine for a few days, then I got the "no cellular data" error. No problem, just rebooted my phone and it was fine. Last week, got the error again "update failed, cellular data not available until ios14 update has been completed." I'm using ios14. When I try updating it, it fails because I'm "not connected to internet" even when I'm on Wifi and have notifications coming in. Tried downgrading to ios13 to no avail. Tried updating on my desktop, still got an error. When I try to reset my network settings, nothing happens. I can't switch my cellular data on/off because I just get an error screen. Spent 2ish hours on Apple support to no avail. My phone was bought in the U.S., living in Korea now. No issues were shown after a diagnostic test, so Apple suggested I get it fixed. Seems like a very technical issue to try to explain in my non-native language. Sigh. Really don't want to have to buy a new phone because of this so hoping Apple fixes the issue soon. Wish I never updated to iOs14!! RIP