Once and a while cashiers will say 'You can not use a credit card to purchase the gift card', but, simplest solution is just go to another cashier in the same store. Done this many times. I've even gone from a cashier, and over to the manager instead (guys/gals in the white shirts), and they run the purchase through fine. In fact, I've never actually had a store manager make this statement to me before, only 'by the book' cashiers.
Also, I have consistently been using the GC's for 'every thing' in the store; Booze, milk, etc. I always go to the cashier with the white shirt, since they are a manager, and they've always 'overrode' the cash register block on accepting the gift cards, without ever even getting into a debate with me about it. So, as far as I'm concerned these coupons are as good as cash in the store.
If ever you get some manager telling you that the coupons are no good for booze, just politely ask them where exactly this exclusion is ever mentioned. They will not be able to provide that answer.
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Now as an aside, these 'Mastercard' GC's no longer work at serve.com due to address validation errors. They certainly did work in the past, and in fact until very recently. Anyone figure out a trick around this? Since serve is now re-linking these as debit cards, the ability to cash out of the GC's has gone up 5 fold.