Unable to perform updates

[Android Question]

I recently purchased the Samsung Galaxy s3 from ************.com. It's the GT-i9300 unlocked phone which I use with Straight Talk with the "unlimited" plan. I have the AT&T compatible micro sim card. I went through the process to change the APN, which I believe to have been successful, as I was able to access the internet without wifi.
Now with the basics established, I ask you my question: Why is it that when I go to perform the update from Android 4.1.9 to the current 4.3 I am constantly receiving the message "Network connection failed"? Even when connected to wifi, this happens.
I've contacted straight talk, and they won't help because I did not purchase the phone from them.
************ says there is no update available (which is false because most of my friends have s3 phones running 4.3).
Geek squad told me to update on public wifi with a stronger connection than my home wifi.
Can anyone shine some light on this?

 

[Rukbat]

Since you're not an AT&T customer of record (Straight talk is their CoR), they won't update your phone. Since ST isn't the crrier (they're the virtual network operator) they can't update your phojne. If you want it updated (bad idea with the S3 - too many bugs), you're going to have to find an AT&T update file and update it yourself.

The good news is that the phone won't keep bugging you to do an update that you really don't want to do.