The network will switch based on the strength of the signal. Does it happen everywhere or only when you are at certain locations ( indoors)?
In Settings --> Connections --> Mobile networks --> phone will auto select the best network signal available at your location.
If this constant switch is a recent happening, try resetting the network connections. Note that this will also clear your stored wifi networks and bluetooth connections.
Hello @maciejireland ,
Could you please report this via Samsung Members app? Then the developers will be able to take a look at this 😊
Have a good day!