Hear audio from incoming calls from Nextel before answering

[Flash_C4]

I don't know if this has been posted anywhere but I haven't been able to find it so don't flame me if this has already been talked about elsewhere. I've noticed something odd every time I receive an incoming call on my Sprint Mogul from someone who is calling from a Nextel phone. Before I ever answer I can hear audio from the caller coming from the speaker on the Mogul. We verified that the caller is not able to hear audio from the Mogul so it is one way. I just freaked someone out when they called me because when I answered the phone I repeated the last couple of sentences I heard them say to the person they were with before I answered. They asked how in the world did I just repeat what they said before I ever answered the phone! It's kind of cool but also a bit freaky at the same time. I couldn't even begin to think of how to explain this one to Sprint so I won't bother trying to call them about it.