I am not saying that the billing is correct, but there are ways to make this happen, Imagine Phone 1 and Phone 22 has call waiting activated, 1 has call conference activated(both are normally activated by default)call from 1 to 2from 1 put 2 on holdfrom 1 make another call on 2, it will ring cause of call waitingat 2 put the original call on hold and receive this oneNow, from 1 conference the 2 callsA possible(very unlikely) thing that could have happened is that when you thought the call dropped, it actually went on hold, and when you dialled again, the person on the other side received the new call w/o disconnecting the old one