*I'm kinda having trouble understanding EXACTLY what the issue here is, but I think I have the right idea. This is just the way I see it, so please, correct me if I'm wrong.
Your device is a Sprint-branded Galaxy S7 edge and you tried to flash AT&T firmware to it? NOT A GOOD IDEA!
Before you perm-brick your phone, do not, I repeat, DO NOT flash firmware to your device that is designed for a different model number. That's exactly how you kill your phone permanently. If you're gonna flash anything at all to this device, flash the Sprint firmware, not the AT&T firmware (Do some googling on your phones model number and you should find your firmware, if you're lucky). In order to get passed the SHA-256 error, download the Modified ODIN from the link below, which is made to bypass the SHA-256 detection. Remember to be extremely careful when flashing firmware to your device. The smallest screw-up can leave you with an $800 brick. Trust me, I learned that the hard way
Odin 3.12 Patched (requires Win-RAR or 7Zip to extract):
https://mega.nz/#!jlIlRYLA!AE0yW7A9gi3236cjRFr7QUJslMj6Pjy-pll6OONfgLk
I figured it out i downloaded the wrong firmware it was for another country with the exynos processor thats why it wouldnt flash back ive flashed back when i got the phone back to att im having 0 issues everything works beautifully even samsung pay