How does DUAL SIM example Huawei 20 Pro?

How does the DUAL Sim example work on the Huawei 20 Pro.
If you insert two SIM cards eg o2 and Vodafone.

Ring both numbers without restarting?

It rings the number which is called.

OK, thought it's just a sim and selects the one at the start of the phone. But that was probably so "duff" earlier.

You can use both SIM cards at once. When calling you can normally specify the number and then have the choice with which number you want to call.

Thank you