Your area may use AT&T or T-Mobile. So the technology is different and not compatible. It could also be your device may not be unlocked. You have to find out with ST to find out why it isn't if you device is unlocked and your area can use Verizon.
It's hard to say, you would have to check with Straight Talk to get a straight answer. You may want to check with Total Wireless (Verizon MVNO) & see if your phone is compatible before giving up.
Even a seemingly perfect phone may not work with an MVNO, even if it works fine with the parent company. My mom's Verizon flip phone was not compatible with Total Wireless. I bought her a phone from Total Wireless that is the same model as the Verizon one. The case from her Verizon phone even fits it like a glove.
MNVO=Mobile Virtual Network Operator-i.e. Boost, Metro PCS, Cricket, etc . . . .
For a phone to be compatible with Verizon, it has to be able to use the correct radios/frequencies. Not all Samsung Galaxy S3 models have the same radios/frequencies.
For example, there are multiple models of the S3, 2 of which I have listed below for comparison. The 2 models, while having the same name have different specifications in the radios/frequencies available in the device.
These 2 models of Samsung Galaxy S3 are not compatible with each other's networks.
Additionally, other models than these are also available.
Recent phones from some manufacturers are including more radios in order to be compatible with more carriers. Current generation iPhones would be an example. Others also have this capability. Unfortunately, the S3 being 4 yrs old, was made before manufacturers started this practice.
While the Verizon variant of the Galaxy S3 has GSM radios in it and can use AT&T HSPA+ / GPRS / EDGE, it does not support the AT&T LTE Band 17. They won't activate that device as such.
You'll want to consider getting a newer device from the S3, for as well as it's been holding up.
Depends. It could be a GSM phone which is not compatible. Sprint and Verizon use CDMA which is what you need.
It sounds like you don't have a sim card. Do you already have a Verizon sim card you are trying to use in a S3 from Straight Talk? If your S3 has the right radios in it, and you have a Verizon sim card, it should work.
If you are using Verizon's website to see if your phone is compatible. I have read many times Verizon will always tell you a phone not purchased through Verizon is compatible. This is not true though.
I learned about this when I researched buying a Nexus 6P.
I Had the GS3 with both carriers. The Verizon GS3 lacks LTE bands for ATT. Because it predates the unlock requirement, it may not be unlocked for domestic use. As liberal as ATT is, my Verizon GS3 would not work on ATT network. The GS4 will work, but no LTE, the S5 will work, has LTE bands, but MMS may not work.
DigitalRules. Many current flip phones have no removable SIM card, and can't move to another network and can't be unlocked. The older they are the more true that is.
smith6612. ATT will activate a phone that will only get 3G and has no LTE bands for the network.
FYI, the ATT LG V10 does not have band 17. LG V10 - Full phone specifications
They may for now. Although I have heard rumblings that they plan to begin the sunset process for HSPA+ / EDGE in the not too distant future. I know Verizon has already begun the process in this area, refarming much of their 3G spectrum as VoLTE begins to climb in use.
There is no plan or even a valid rumor that ATT is planning on sunset for 3G. ATT is currently turning off 2G and it will be complete by the end of 2016.
AS I said, I am currently with ATT and know what their BYOD policy is, it's very liberal.
Actually they all plan to, but it's farther out as they need to slowly phase it out as a lot of people still use 3G only devices. It is speculated by 2022 all US carriers will run solely on LTE or faster technology.