If AT&T cannot unlock it's own iphone.....

[Aqua Pro Builder]

Duromega

What type of protocol is an AT&T iPhone 4?
What type of protocol is a Verizon Note2?

Here is what I found for my Verizon Note2:
Network
4G LTE, CDMA/1xEVDO Rev A, (800/1900 MHz)
Global Ready (GSM/EDGE: 850/900/1800/1900; HSPA/UMTS: 850/900/1900/2100 MHz)

so I assume this phone can be used on the GSM network when they unlock it, correct?

 

[duromega]

Duromega

What type of protocol is an AT&T iPhone 4?
What type of protocol is a Verizon Note2?

Here is what I found for my Verizon Note2:
Network
4G LTE, CDMA/1xEVDO Rev A, (800/1900 MHz)
Global Ready (GSM/EDGE: 850/900/1800/1900; HSPA/UMTS: 850/900/1900/2100 MHz)

so I assume this phone can be used on the GSM network when they unlock it, correct?

correct !
your Note 2 from verizon is GSM capable so if you get your phone unlocked you will be able to use it on any GSM carrier worldwide.

 

[duromega]

the CDMA GSM dual band Verizon iphone 5 works with an ATT sim card. There was no jailbreak at the time and I had the 4G service.

What you mean to say is that another CDMA carrier cannot be configured to that iphone.

yes! your verizon iphone 5 is WCDMA (worldphone) CDMA network and GSM network capable; sprint and verizon iphones (WCDMA) are GSM capable and verizon iPhone 5 comes "GSM Unlocked" from the box it can be used in any GSM network worldwide, BUT for CDMA network it only works with Verizon
Why? because iPhones purchased by Verizon are manufactured pre-programmed with an exclusive MEID # (Mobile Equipment Identifier) that will activate only under that specific carrier
sprint iphone 5 same situation a specific MEID that only activates on sprint
but sprint phones doesn't come "GSM unlocked" like verizon ones
on sprint you're able to unlock your phone calling costumer service and requesting unlock (and your phone will work with any GSM carrier only outside of the united states)

there are 2 models of iPhone 5
GSM A1428 (this one is not CDMA capable) AT&T
CDMA/GSM A1429 (verizon/sprint)