I never realized that giving out my zipcode would be an issue, so I would give that out, when asked. I'll stop doing that now. But I do generally refuse to give out my phone number, and I've never had them question me further. They just ask something like, "And your phone number?" or "May we have your phone number for our mailing list?" I just say, "I'd rather not give it," and they usually just say "Okay!" and proceed with the transaction. I always figured that zipcode was generic enough that it didn't matter, but I didn't think about the fact that I'd also given them my credit card. Although with my name, I doubt they'd need my zipcode in order to look me up by name and add me to their mailing list if they wanted to.