When you disconnected the call, the system didn’t disconnect the call completely which is why it drained the balance for the duration you see.
I had same problem 2 times.
One time they solved my problem and they credit back my balance. Second time, still waiting answer???????
So, you have to check carefully at Call logs (outgoing) and view recently International calling, they will charged you different duration.
Anyway I'm using Skype now, and never has a problem, cheaper.