I routinely get my money back, and other coins as well. You might be able to do the same thing. (Note: I used to fix this stuff for a living, so I learned how they work.)
Step 1: How they work
Step 2: Push the Coin Return knob -- HARD and FAST!
Instead, flick the return knob hard and fast, over and over as fast as you can, and try to fling the coin beyond the edge of the magnet. The coin will drop in to the coin return like it's supposed to do. Repeat as needed. If that doesn't work . . .
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.
Step 4: If that doesn't work . . .
Therefore, if all else fails, look around for a refund source. If you tell the owner, they'll likely return your lost money. If you have vending machines at work, there's probably a process for refunding lost money. The guy who fills the machine knows how much stuff he put in there, and how much money he took out. If there's too much money, he knows someone was cheated (and may start banging on his expensive equipment if he doesn't resolve it).
IMPORTANT ! ! !
There are (probably true) urban legends about people who try to get product out of those 'twist a big silver wire screw and deliver one item' vending machines by tipping the whole machine forward so everything falls out. Those same stories tell of people who DIE when they get crushed under the thing. Just don't do it. If you think they're not heavy, just try to move it 1 inch where it stands. Not a chance.
However, if you do crush your hand or something, you might be able to collect workmen's comp if you're at work. (Ha ha, just kidding.) Don't do it. There are a few things in life worth risking your hand over; three free bags of chips is not on the list.
Step 5: Free video games!
Check each coin return box as you walk by them and sooner or later, you'll find coins someone has unknowningly left behind. They may be bent, foreign, or just fine. Video games are best, since players often don't know how many coins they need to get a game started, then get distracted playing the game.
Don't forget to try these coin return tricks on machines marked 'Out of Order' as they may be turned off because somebody lost their money in them!
This is my first instructable. I hope you enjoy your free money . . .
P.S. My next one will be KILLER !!!