Friend's and my phones calling eachother. A Mystery...?

[ASurprise]

For the past 2 nights between 3:10AM - 3:30AM my Sprint Touch has been getting calls that indicate the ID as a friend in my contacts list. This happned to me again last night/this morning, however my frriend also revieved a call indicating the ID was my phone. What's stranger still is that we both recieved the calls within 1 minute of eachother, and we both heard a garbled unintelligible voice saying a few words, then the call ended.... Anyone hav any clues ss to what could possibly be going on? I'd really like to know. and thanks in advance for any advice.

About our phones: They're both Sprint. Mine is a 2 month old Touch/6900, his is a 2 year old 6700.