If you’ve been moving your SIM card from phone to phone over the years, you might inadvertently be preventing your current phone from taking full advantage of 5G connectivity. Cellular carriers aren’t always forthcoming about what will and will not work, but at least in the US, AT&T, T-Mobile, and Verizon all make noises about how you need a 5G-capable SIM card to use the latest and greatest 5G technologies. The solution is simple: stop by a carrier’s store or contact them to ask for a new SIM. It should be free and will take just a minute to install once the carrier support people have configured it to your phone number. Precisely where the SIM card slot is on your iPhone varies a bit by model; Apple provides full instructions.