Cannot switch iphone 7 from AT&T to verizon

Read here about compatibility- it can not be done

There are two iPhone 7 models: model #A1660 (Sprint, Verizon) and model #A1778 (T-Mobile, AT&T). There are also two iPhone 7 Plus models: model #A1661 (Sprint, Verizon) and model #A1784 (T-Mobile, AT&T). Each model number supports different technology and will only work with select carrier networks.

https://www.whistleout.com/CellPhones/Guides/Will-my-iPhone-7-7Plus-work-on-anot her-carrier

You cannot convert it. one is a GSM and one is CDMA. The hardware is different.

You are limited but there are newer phones like the Xs, Xr, and Xs Max that supports multiple carriers.

rbarnett1935 wrote:

So I'm limited in what carrier I can use. Is this true with all iphones?

No, you are limited to using only GSM carriers. Which is all of the carriers in the world except for Verizon and Sprint in the US and a couple of carriers in India.

You can't make it compatible. Verizon is a CDMA carrier, the AT&T iPhone 7 does not have a CDMA radio.

Here is an article that explains the differences -CDMA vs. GSM - What's the Difference?