Do I remove my SIM card from my old phone
Do I remove the SIM card from the 7+ before sending it back as a trade
iPhone 7 Plus, iOS 14
It’s your choice. Personally, I have traded several iPhones over the years using Apple’s Buyback program and have never removed the SIM card. But I do carefully prepare the traded iPhone as follows:
What to do before you sell, give away, or trade in your iPhone, iPad, or iPod touch - Apple Support