This is not entirely true.
The Verizon iPhone 4S is essentially a GSM and CDMA code added to the baseband.
I have a gevey sim being used in the Verizon iPhone 4S and it works on T-Mobile.
An alternative to not having a gevey sim is to have Verizon unlock the iPhone 4S. Once unlocked, disable the CDMA antenna so it will only default to the GSM signals. To disable the CDMA antenna, 2 plist files must be removed. For some odd reason, both Sprint and Verizon iPhone 4S have each others' antenna file--just remove both of them, or better yet, back them up and move them to a different folder. This way, if you want to return to verizon without having to wipe the phone with iTunes. Needless to say, this would require a jailbreak to access the filesystem of the phone.
here is from another site:
How to Unlock Verizon and Sprint iPhone 4s ios 5.01 with REBEL X-SIM - GSM-Forum
- Connect your 4S with iFunbox
- Go to /var/wireless/Library then delete file carrier_310VZW_20404_11.x.plist ----the Sprint file should be carrier_310SPA_20404_11.x.plist
- Go to /System/Library/Carrier Bundle/iPhone delete folder Zeppelin_US.bundle and delete your sim card carrier
of course do not just delete the files. back them up by moving them to a different directory or just rename them
I have done file renaming in addition to using gevey sim imposer since my phone isn't unlocked. If unlocked, you'd still need to move/rename files.
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Some people complain of the lack of "Enable 3G" switch in Settings of the phone since being stuck on 3G without the ability to turn it off will drain the battery quicker. This is a feature unique to only T-Mobile and AT&T phones. A workaround is to look for an app on Cydia called DropCallEliminator. DropCallEliminator will enable EDGE as the precursor to 3G--it retains internet connection while conserving battery.
This is not entirely true.
