Sales receipt

Next week my contract is over with AT&T and I want to unlock my iphone 4g. I bought my iphone from an apple retail store in walnut creek, California. Unfortunately I lost my sales receipt. If I go to that apple store could they provide me a hard copy of the receipt? Also here is the thing, last year i had to get my iphone replaced because of a hardware defect and I got a replacement from that very same store. I managed to keep onto the receipt for the replacment. I am just worried, given At&t's horrible track record on phone unlocks, that i might be denied. Also for some strange reason every time I call 1800-my-apple none of the sells reps can here me. I tried using calling with my iphone, my land line, my friends phone, and even google voice. It seems they can't hear me. Is apple having tech difficulites on their part or am I.....black listed lol?

Btw it's 8:35pm on a sunday and my last failed attempt to call them was10 mins prior to writting this.

Thanks