Using the Samsung S4 (SCH-i545) with SK Telecom in South Korea
A relative is having trouble doing this, and I'm fairly certain it's doable, but need some advice.
Apparently, after going through the whole process through SK Telecom, the "Not a Verizon SIM card" popped up on her screen and they told her that she needed to contact Verizon in the U.S. and get her phone unlocked.
Multiple people at Verizon have told me that the phone comes unlocked and that there is no longer a 60 day period before the phone becomes unlocked. So it's not an issue of the phone being locked or unlocked.
Then they said that the frequency might be wrong and that the phone needs to support W-CMDA 2100 to work in Korea. This took some time figuring out, but as I understand it W-CDMA 2100 is also supported by the phone, but is listed as UMTS/HSPA+ 2100 if it's a Verizon phone. And it seems for data, that the LTE they use in Korea is the same as what Verizon uses in the U.S. The Verizon Iphone 5/5s are able to make use of LTE in Korea which gives me confidence that a Samsung LTE phone through Verizon should be able to do the same.
Has anyone else gone through the experience of setting up their Verizon S4 for use in Korea?
Re: Using the Samsung S4 (SCH-i545) with SK Telecom in South Korea
I am also trying to figure a lot of this out too so I can only share my understanding of my findings thus far...
Since you said you had a Verizon phone, I assume this means you have the model# i545. My conclusion is this phone cannot work on any of the major Korean phone carriers (I still hope to be proven wrong). You might need to dig and use some other 3rd party option as an alternative to get it to work, but I didn't bother checking those options as they are probably more expensive than renting a phone.
There are 2 reasons for my conclusion:
#1) Korea uses CDMA (I know Verizon is CDMA also, but more on that in a bit)
#2) the LTE frequency for Verizon's GS4 does NOT match any of the major phone carrier's frequency in Korea. (other GS4 models may have the appropriate frequency*, but not Verizon's model)
*You might think that you could just buy this 'other model GS4' and go along merrily in Korea and on Verizon in the US, but be warned, Verizon will not activate your 'other model GS4' on their networks because it is not approved. More on this in a bit also)
I will address #2 first because it is a short answer, which I'm sure you have already figured out. In order to operate via LTE, you need to have the phone able to work on the correct frequency. The Verizon GS4 operates on 750MHz and 1700MHz only , while Korea's main telecoms (SK, KT, LG) do no have these frequencies. I found the frequency information here [Only registered and activated users can see links. Click Here To Register...] . This is why Verizon's iPhone 5c and 5s CAN work over LTE in Korea because Verizon's iPhone model has a matching frequency on which to operate over.
So back to #1, Korea uses CDMA.
So the reason why this is a problem, despite Korea and Verizon both working on a CDMA network, is based on how they store identifying data. The identifying information is how carriers can keep track of what phones are on their network. GSM phones store this data on the SIM card so as long as you have a carrier approved SIM, you are good to go on GSM. CDMA however stores this data on the carrier side, meaning you need to get the phone registered and stored in their system before they let it on the network. Unfortunately, most CDMA telecoms will not just allow any old CDMA phone onto their network; it has to be an approved phone. What this means is Verizon CDMA phones technically could work on any CDMA network with matching frequency, but the reason it wont is not because Verizon locks you in, but because other CDMA carriers will lock you out. This is why I issued the warning about purchasing an 'other model GS4.' Verizon will not activate a GS4 unless it is a model i545, aka the Verizon GS4, and similarly why bringing your Verizon GS4 to a Korean phone carrier will result in them not activating your non-approved GS4. So for your situation in Korea, unless you can get one of the Telecoms to register your CDMA phone as "ok" on their network, your phone cannot get service.
If you were in a country like Taiwan or in Europe, that has GSM services, you would most likely be able to pop in a SIM and be good to go, but, since GSM is not an option, LTE is not an option, and CDMA most likely not an option, this cuts out all possible avenues for phone use.
No GSM = no 2g/3g/4g service
No CDMA = no 3g/4g service
No LTE = no 4g LTE service.
My conclusion as of now is Verizon's SG4 model# i545 can't work in Korea with a Korean phone carrier. Good Luck!