Talk:Mexico/@comment-72.179.29.194-20151105204358/@comment-24682153-20151107175609

All operators in Mexico are mostly GSM-providers like AT&T or T-Mobile in the US. Verizon is a CDMA operator. You can't use a CDMA-only phone on GSM. Only so called "world phones" with SIM card slots for GSM-SIM cards can be used in most countries outside of the US. Check our article CDMA in the United States for details.

When you check the specs of your iPhone 4 e.g. here, you will find out, that it's not a "world phone". It's either GSM-only (sold for AT&T or T-Mobile) or CDMA-only (sold for Sprint or Verizon) and doesn't have a SIM card slot. You at least need an iPhone 5 to cross the systems barrier.

There used to be CDMA coverage in Mexico, not on Telcel, but on Movistar and Iusacell. But this is phased out like in Canada. A very limited CDMA rest coverage is maintained for the small number of CDMA users still in the country and for roaming of old Sprint and Verizon phones like yours. But as Iusacell have been taken over by AT&T, this is going to phased out soon too.