I don't do the wrong number thing multiple times. I'll waste a bit of time on the phone just to pull off being "natural."
Call 1: "Sorry, I think this is the wrong number."
Call 2: "How late are you guys open?"
Call 3: "I was thinking of dropping by, but can't seem to find the right directions. I'm coming from (Place)"
Call 4: "Is Tina there? No? Isn't this Brownley and Associates?"
After I'm given the green light to hard-target my target, I leave a voicemail saying "Hi, this is (Name) I'm calling for (Target) We spoke a few weeks ago and I've just now been able to get back to you. Please call me back at (Number)"
Doing it that way, they just think their memory is a bit fuzzy, but they'll never say they don't remember you. They'll try to fish in that first phone call, what your previous interaction was, but that's it.
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Plan the work. Work the plan.