Cellular data intermittently not working with full 5G signal strenght on iPhone 13 Pro

It happens several times a day. I see full signal and 5G coverage, I hear the beep of an IM message or see the badge on a mail app, however, when I open the app, there is no new message. If I check, there is no network by Speedtest or any other app. But there is full signal strenght and somehow the phone knows that I have 3 new mail, so maybe the data loss is partial.

If I turn on Airplane Mode and toggle back it again, it solves the problem. However it is extremely annoying five to ten times a day...

Apple please help, this is not a carrier issue since I experienced it while roaming - but not on Wifi.

thanks,

kk