Maybe just an awkward sales agent, or they thought you were mad at them for in their mind trying to help. I decline phone number and zip code all the time. Also been using someone else's phone number at grocery stores for years -- started by mistake. I don't care about accumulated points or whatever but discounts at grocery store are pretty significant for me.
But I understand your frustration in general. Keep up the good fight :)
I wonder if it would take more or less time with auto-complete.