When calling collect, you do have an option of what carrier to use.
E.g. remember all the old commercials, 1-800-call-att versu 1-800-collect etc?
I got burned on thsi once too, on my way home from a late flight, called wife for about 5 minutes.
Got the bill, $35. WTF?
Well it turns out the number I dialed, in my tired sleepy delerium, was 1 digit off from 1-800-collect or whatever I intended. I didn't realize this, and was routed through another company who "squats" on similar numbers just to catch guys like me. Perfectly legal, just a little unscrupulous.
Oh and re: $7 calls from an airplane - I *love* their slogan - "It's not the expense of the call... it's the expense of NOT making the call."