Basket Interference

[jref]

Last night I had a varsity game in which I called a foul in the act of shooting on the defense (team B). The ball is half way down, when Team A commits BI by touching the ball in the cylinder. I wave off the basket and give the shooter two shots. The coach of Team B argues that only one shot should be given because of the offensive BI. I stuck with two, I believe I am right and I told the coach the only way a free throw can be taken away is by a lane violation. I would appreciate your input,thanks.