The SIM card in the flip phone is incompatible for use in a 4G LTE phone. You need to get a new 4G SIM card. You need to get a phone that is compatible with the Verizon Wireless network.
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Choosing the right device is important. Let's explore your options. What do you mean by 'certified iPhone'? Which specific iPhone are you interested in? Will you purchase the phone from Verizon Wireless? As for the Sim card, Ann 154 was correct in that you will need to get a new one.
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Adding onto this, it seems you don’t need the fanciest or most powerful iPhone since you’ve had an old flip phone up until now. Also, flip phones tend to be relatively small so it looks like you’re wanting a more compact iPhone. Is this correct? If so, my recommendation for you is to purchase a new iPhone SE. It is apple’s most affordable and compact iPhone that is still in the current lineup of new iPhones and has decent graphics.