Phone calls in '04 X5?

Twice now I have been driving with the radio on and the phone will suddenly start ringing. The phone isn't activated but BMW assist is.
The second time, someone answered. I tried to find out where they were but they were confused because I called them.
My 2nd service is coming up soon so I'll bring it up with the tech then but I wanted to see if this has happened to anyone else since the tech might not be able to repeat the problem.
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