It can go both ways, but it probably depends mostly on the size of the business. With a larger business, you would probably be more inclined to set up a meeting, but with a small business, where someone who makes financial decisions is more easily accessible, it is more reasonable to walk in at any time of the day. Also, if the business you are approaching is a potentially very large sponsor, perhaps a potential main sponsor, you might want set up a time to make a presentation with a group of team members at the business.
I can’t say from my mind what exactly is said in a phone conversation as such, but I would suggest that you, as a team, have a meeting and develop an organized strategy, and appealing phone pitch to deliver to the business. Give them something that draws them in, tell them that they have no obligation to give now, just that you want to give them this presentation. Try not to give off a real “telemarketer-y” vibe, either. Remember that it is easy to hang up on, or say no to, a voice on a phone.
Even if a business is unwilling to talk over the phone, remember, they can always be visited in person. If you can’t directly talk to a manager-type figure, I would suggest making fundraising packets, and have these be passed on to such a person. These might include information about the program, about your team, about how to contact you if interested, and about how one might donate to your team and the benefits of doing so (helping a local organization, advancing engineering education in youth, advertising space on shirts and bots, etc.). These packets can convey what a phone conversation simply can’t about this program, and may be a better tool in this situation.
Some businesses do turn you away, in good times and in bad. In that case, just keep looking, and don’t get down on yourselves. You’ll find someone out there, but persistence, along with planning, is key.
Good luck, and I hope this helps!