Generally, one phone book will have only a couple different area codes. If you are using a PAO from 00-99, then I would combine the area code with the first digit and make that one image.
404-1, 404-2, 404-3, etc. are all different images. Then you are left with 6 digits that will fit perfectly with a PAO from 00-99.
I’m not sure that you could use locations for a decent sized city. Your choices are to turn the numbers into locations which creates 10,000,000 + [number of area codes] different locations; or you could turn the people into locations, which for me in Dallas would be 2,412,827 different locations. One number looks slightly better than the other, but neither is even approachable. It seems to me that you would need to turn the name into an image and create an association between the name image and the number image.
William Thompson could be an a thumb with a halo around it poking out of an apple. William -> William Tell -> apple. Thom§son -> Thom -> Tom Thumb -> Thumb -> son -> sun -> sun-like halo.
Now when you are quizzed: What is William Thompson’s phone number? you should conjure up the image and–somehow–associate that with the PAO. I’ll leave it for you to figure out the association step until I ever decide to memorize a phone book, which I doubt will be any time soon.
I would suggest that you memorize a dictionary. The process is a bit easier. There is a clip on this forum somewhere of a Chinese man explaining the process.