What is right way to handle?

[oldschool]

Will try to be clear on situation. Team A is passing ball inbounds in backcourt on baseline. Team B is pressing. I am the in posision near half court. Lots of activity near baseline. As A attempts to pass I glanced and saw she stepped over the line. I look at my partner to see if he saw it and he was looking out for contact on the inbound pass. He did not call it. What would you do? I assume this is out of my primary. I know I should be watching the other players but there was so much activity up front my eyes wandered in that area. I am a 2nd year man and want your input. Thanks