I'm not saying you should say yes to be agreeable. Just be polite but firm. I would say something along the lines of "I don't want to give out my phone number

I'm not saying you should say yes to be agreeable. Just be polite but firm. I would say something along the lines of "I don't want to give out my phone number sorry." or even just shaking your head back and forth works. "Do you have a phone number" "No" comes off as you being irritated and will make the staff member feel like a dick for just doing their job. I'm not saying you must always be polite. If somebody is being a pushy asshole push back. However if you can take a few seconds to make a minimum wage drone not feel as bad about their job its well worth it.