So you had to open the phone and replace the SIM card for different uses? That would not be practical for me as I often have simultaneous calls on two phones. Yes, my business life can be that hectic. It’s a good idea, though.
No, there’s slots for two SIM cards. I have one O2, one Vodafone. Two separate numbers. Just pop in both your SIM cards in the two slots, and you’re good to go.