Big Guy vs Little guy

A1 is 6'5" 260lbs and B1 is 6' 160lbs. Shot goes up and A1 just walks his way into the lane for a rebound. B1 is boxing out and obviously without actually pushing, A1 is able to get himself into a better rebounding position.

Do you have a foul? B1 is entitled to the space on the floor where he is standing. A1 just uses his weigtht to get to a spot.

I called A1 for the pushing foul(over the back). My partner felt it was a no call.

Your thoughts.