Galaxy S6 is not updating to 7.0
Hi everyone. I have just bought a Galaxy s6 At&t and it is running Android 5.1.1 Lollipop while it should be running Android 7. I have tried to update it but it says that "Current software is up to date". I checked At&t website about S6 update. It says that to update your device your baseband version should be G920AUCU7ERB1. But my device has baseband version G920AUCU3BOI2. Please help me updating my device. Thanks in advance.
Note: My region is Pakistan.