You NEED to know the decision maker's name and sound like you EXPECT to speak with him, and make the gatekeeper question her/his authority. If you can make that person doubt their authority and feel like they are preventing something important....you are well on your way to getting the decision maker on the phone 1 to 1
Very easy in concept, but much harder in execution when they can hear your voice if you slip up and try to correct yourself when you realize you slipped up. On the other hand, the tone of your voice and elevated speech at certain points to emphasize something is also going to work to your advantage.
Before you call, do your research and learn about the person you want to reach. Most people trying to get past the gatekeeper don't do this. You might even want to research the gatekeeper too. As you said, you're targeting an owner with 50+ locations and who also has contacts, so it's worth your time to get this right.
When you call, you better have a good strategy for how you'll deal with different situations. Are you going to play on having met the owner in passing at say... their kid's sports game or dance recital and following up with them? If so, you better know if the owner regularly attends those events.
If the gatekeeper gets a little skeptical, how are you going to handle it? It's good to know about them too so you can sound more credible and act like the owner mentioned them and their personality in passing to you in the past.
There's lots of ways to tackle it and it takes practice to switch tactics in mid conversation on the phone since you can't see their facial expressions.
The key to getting in to talk to the owner and selling a story is to not commit to something. You want the person to know just enough to assume something. When they assume, there's doubt about if they were right or not in having met you in the past. That lets you in.
You want them to remember you like Zed from Men in Black said:
You'll not stand out in any way. Your entire image is crafted to leave no lasting memory with anyone you encounter. You're a rumor, recognizable only as deja vu and dismissed just as quickly. You don't exist; you were never even born. Anonymity is your name.
After you're in, sell them and leave a lasting impression. They won't question it.