Hi guys, I also have the S9+ dual sim and had the same problem yesterday. Sorted by turning off VoLTE calls from Settings/Mobile Networks and also Data Roaming switched off. And now the internet works just fine when I leave my wifi from home. Let me know if it worked for you also...
I can confirm switching off VoLTE calls has temporarily fixed this issue for me which coincidently started after the latest update from Samsung which was apparently for Google now.
I hope Samsung are listening to this and get a fix out sharpish.
And for those asking, my phone is S9 Plus 128Gb single sim version.
I can also confirm that switching off VoLTE has fixed the issue (for today atleast!). Hopefully this is a bug Samsung can iron out in their next update. I will let customer support know that this is an issue
I've had the same ridiculous issue and have been been scouring the internet for the last 2 hours looking for an answer. I've come across this post and it was the only thing I've found that's worked so I've set up a Samsung community account just to come on here and say thanks Anghelu2001!
Having exactly the same problem:
1. S9+ dual sim - SM-G965F
2. Yup, downloaded 20th June
-This might be causing the problem because in Settings>Connections i dont see disable voWifi. -> wifi calling is under call settings (open dialpad, 3 dots to select settings, wi-fi calling down bottom)
3. Sim 1 - 3, Sim 2 - O2
Just disabled voLTE so going to check to see if this is the cause.