This was my experience yesterday being the 17th of May 2012. At about 7.23 am, I received a call on my MTN line from a friend of mine whose number was actually stored on my phone by name CHARLES (An Airtel subscriber), to my greatest susprise I had a strange voice apparently that of an Igbo man and not that of my friend Charles, calling the name "Ogochukwu"... Few minutes later, I received the 2nd call from that same number but this time It was a voice of a Lady I heard her saying "Madam where are you" "I am at home"..
I called back the number (My friend Charlie) bu the call was not picked.. Later Charlie called me and I asked him why he gave his phone to strangers, He Charlie said he too was surprised at the fact that the first time he called my line someelse picked it.
To cut the long story short, our calls where being exchanged and sent to the wrong numbers other than that dailled which is quite embarassing for big networks like Airtel and Mtn..