Attention:using cell phone+ phone card call back to china

Hi, Just to reminder you because some unhappy things happened to me.Maybe csomeone has the similar experience.
I use cell phone call back to china through a transition insiae the USA from few months before, only this time I got a big fee bill from Cingular,they told me I directly dial the china. then I looked careful in my fee bill. Cingular charged me both of the long distance and international call (in the fee bill, both of the call started at 8:42 pm, and the first one lasted for 2 mins).then I called them, the supervisor give a 50% discount of the charge.And I asked the supervisor to wrote me a letter to explain why this situation could be happened (one phone two calls at the same time). He said he is no ability to write the letter.Is this true? I doubt it because I told them I have the right to sue them.
Anyway, if you use cell phone call back, now the first thing is to call the phone company to cancel the internation call.

Good luck