You should power off/on the device when switching SIM cards. A hot swap is not supported by Lumia 1520.
- What is the WhatsApp messenger and where can I download it?
- Is Microsoft account required for my Lumia phone to work?
- I have forgotten my Microsoft account password
- What to check if I can't sign in or create the Microsoft account on my Lumia phone during the initial setup?
- I cannot find the built-in camera app from the application menu after the Denim update, why?