Understanding Japanese

My hearing ability in Japanese has never been that good, but for the past decade or so, since the only Japanese I really listened to in NY was my husband's, which was often grammatically incorrect, it has deteriorated considerably.

So I go to a supermarket named "Peacock" and am asked something by the cashier. I ask her to repeat and she obliges. I still can't understand.
In NY, when the sales assistant asks something when you are paying, they are usually trying to sell a credit card.
I guess the correct answer in the Peacock situation is "no" as well.

So from then on I just say no, whatever I am asked.
I don't know what I am being asked anyway, so what have I got to lose besides some opportunity to open a line of credit?

Well, I finally realized after several months that I lose the privilege of getting a plastic bag for my stuff.
Why didn't I even notice this for so long??