upgrade device via costco website: how to submit rebate? Automatic?

I upgraded my device via costco website beginning of this month/Aug. Checking on " promotions.t-mobile.com/submissionstatus " on my line indicate "no rebate found". I called t-mobile rebate 1-877-311-8853, and was told it's "automatic" submission. I'm confused because the status said not found, but yet it's automatic. So how do I submit my rebate? or is it really automatic? (if so, why is the status is not found?) TIA