Airbus330:
Dun bother la... since got alot of people like to "fully utilize" their free incoming, just take note of that person and dun call back. SMS that person
"(*default message: looking for me? pls call me back")
(optional: My hp keypad spoilt cannot dial)

I notice its from gals most of the time ( from my past experience )
If dun wan to pay to call, y bother to call people or even take a hp in the first place.
Although mine is also free incoming.. but every month still rack in about $150. If you got to make the call, just do it. ( And my company only sponser 50% )

Just dun call them back if they use this tactic. If its urgent call, they wun do this.
If you dun call back and they ask y, just tell them you were bz or something lor....