iPhone 12 PRO loses cellular internet after WIFI usage

Hello,

I have iPhone 12 PRO and there is an issue where I leave wifi network area, and provider internet is not working.

Seems like there is a software bug that prevents phone to use cellular data once wifi is lost.

What is the reason for this issue? This is very annoying considered the amount of money I paid for a flagship phone.

Please advise,

Thanks,

Lior