Solved! Go to Solution.
I was stuck on 3G on my S10 for several days and no matter what I did nothing restored my 4G service.
Until I saw this guys post I'm replaying to. 😄 I put in the code (##72786#) and it updated some stuff and restarted & reactivated and my 4G LTE service is restored! After hours of searching your post was the fix.