I have two iPhones. iPhone SE and iPhone 7. Both Verizon Wireless. The Tracfone SIM card is activated on AT&T network. When the SIM is the iPhone SE, I don't have to do anything and it has zero problems picking up 4G LTE. Signal is 3 or 4 bars. Running speedtest.net app, I get at least 30mbps down. However, if I take the same SIM card out and insert it into the iPhone 7, it will only pick up 3G. (speedtest app only shows 4 to 5mbps down) Yes, I did enable 4G in the cellular menu. If I put the SIM back into the iPhone SE, then the SE picks up 4G LTE. The iPhone SE was purchased from Verizon corporate store. Model A1662. I've been using it for a couple of months on Tracfone 4G LTE without any issues. Like I said, the speedtest.net app always gives me around 30mbps. The iPhone 7 was purchased from Best Buy on a Verizon DPP plan. Model A1660. (since Best Buy iPhones are on Reseller Flex Policy, it's the same as the AT&T model... the phone was initially activated at the Best Buy store using a new Verizon SIM card) if I put a postpaid AT&T SIM card in the iPhone 7, it immediately goes to 4G as soon as I start the phone.... Is there something I'm doing wrong? Thanks!