Return phone to Apple store, subsidized price restored immediately?

[BD1]

If I returned an ATT subsidized iPhone that I purchased from Apple.com to an Apple store how quickly does ATT get updated to return to my subsidized price? Is is immediate?

For example, I ordered the 6 and if I want the 6+ but Apple doesn't have it in stock but I can get it somewhere else. Can I return the 6 to Apple, go to the store that has a 6+ and be able to buy the 6+ with the subsidized price? Are the ATT systems updated this quickly?

 

[Gooberton]

Nope. Last year it took nearly a month. I called att every day nearly

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And I should mention they told me it was restored instantly but when I went to places they wouldn't sell it to me cause it didn't show in there system for the whole month