Hi @Joansie
Check mobile data is turned On in your phone and that no usage limit has been set in your settings.
First try turning your sim card off in your sim manager settings then turn the phone off and on ,and then go back into the sim manager and turn the sim back on.
If that does not help then in your General Management under reset you can reset the network settings.
You could also try the physical sim card in the other sim slot assuming your not using an e sim.
The issue could be your mobile phone account or the network itself.
Check any network checkers.
Also if you are able to then try your sim card in another phone.
And another sim in your phone.
Your network can replace your sim if required which is called a sim swap.
There is a diagnostic tool found in your Samsung Members App.
If I can be of any further help then please don't hesitate to ask. 😎
Daily Driver > Samsung Galaxy s²⁵ Ultra 512Gb ~ Titanium Black.
The advice I offer is my own and does not represent Samsung’s position.
I'm here to help. " This is the way. "
