[AC Question]

I found *99 on my caller ID

[VidJunky]

Is it for an outgoing or incoming call?

A quick Google showed that this code can mean that the call was being recorded or on the Sprint network that a feature was attempting to be turned on or off. Since you have the device and haven't given much information I would suggest you Google it and see which of the results most closely fit with your situation and go from there.

Post back with findings or if you want more help.