You can trade in at the store no matter if you bought in-store, online, or over the phone. They can look up your account and see that you purchase a turbo and will apply the promotion to your trade in. Like the previous poster said, be confident, tell them, 'I ordered the turbo online/over the phone, I'm here for the Turbo's promotional trade in.' They'll ask if you want to applies the credits to your account or use it to buy accessories, or gift card. I chose to credit it to my accounts cuz I can always get accessories later on or else where for better price.
I ordered online and have not received any text or email with the promotion code, got tired of waiting and walked into the store to do the trade in, no question was asked, a 10 minutes process.