Step 3: You'll need a tool
You need something to force all the coins further through the coin acceptor mechanism. Consider anything stiff enough to take some abuse, but not much thicker than a quarter. (Actually, whenever I want to find something that no one will miss, I tend to go through the trash. That way, no one will complain that you broke their favorite such-and-such when you bend it into a knot.)
Stiff wire, folded cardboard, plastic tableware -- look around.
Push your tool into the coin entry. If it's jammed right to the top with coins (like mine was) you'll push the whole stack and force some out of the other end.
Hit the coin return as described above.
Repeat as needed.
I got over $5 in change out of the pay phone, and, when I was done, used some of the money to make a call.