That is odd for sure. Welcome to Android Central forums. unfortunately we may have more questions than answers on this one but we need to do some troubleshooting.
Does the phone still function as a phone? Are you able to make calls?
How you you trying to connect to data? WiFi / Carrier / ESP? Obviously the last one is a joke but it sounds like you're talking about carrier data, does WiFi still work or are you unable to connect to anything through the device?
Does the device show any connection at all? You say you still have a signal but at what strength? 4 bars 1 bar for cellular, 4G, 5G, 5GUW for data?
Since it is affecting the phone and not a specific app it would be difficult to recommend any cache wipes or data clears other than a partition cache wipe. You'll have to boot into your bootloader which is some combination of holding the Vol - or + and the power button while powering on the device. Like doing an old school factory reset but we're not factory resetting, there's another option there to clear the partition cache. No pain.
You can also try to reset your connection settings. In Settings>General management>Reset>Reset network settings. This might sting but shouldn't hurt too much.
I don't remember the IP rating of the S8, but did it take any damage? A drop /fall or take a swim within the last week or so? It might need to see a repair center if so.
That's really all I have. Perhaps your answers to the other questions will inspire more ideas from myself or other members but I'm drawing a blank. I mean obviously you've paid your bill and have service, at least I assume you wouldn't neglect to tell us that. Let us know what you find.