If I switch a SIM card from an iPhone to an Android, then back to the same iPhone, will data be lost? I want to take a SIM card out of an iPhone 7, stick it into a Samsung Galaxy A30 for a day in order to make calls from that A30, then switch the SIM card back to the iPhone. Do I need to back up the iPhone's data before doing this, or will it all still be there when I put the SIM card back?
No data is lost on an iPhone when a SIM card is being removed or inserted.
The only thing to keep in mind: You might need the SIM PIN (if there is any set) to use the card in a new phone.