Jesus, what's up with trying to scam extras and discounts AFTER you have already bought the product?!
I can fully understand leveraging different salespeople against each other to get the best deal out of however many different stores, and then buy the best offer -- but seriously; threatening return of the goods for refund unless they kick a little extra your way after the fact is borderline psychotic.
I run a retail business, and this stuff never ceases to amaze me. And you're lucky you get a pushover rep on the other end, because I instruct all of my sales team to call the bluff and ask for the items returned for full refund. Then that person is blacklisted from future orders, because customers like that are high maintenance and are never worth the dollar to hassle ratio.
A special is a special. A sale is a sale. If you miss one by a day or so, then it's just bad luck. But keep in mind that you never handed over a cent more than you were willing to pay, otherwise you wouldn't have paid for it un the first place and would have waited for a sale!
Sorry for the rant, but the sense of entitlement these days is out of control. Everyone wants something for nothing and they want it yesterday.