Triple integral volume

Hello, the question asks me to find the volume of the region above $z=\sqrt{x^2+y^2}$ and $x^2+y^2+z^2=2az$ .

I get to the integral $\int^{2\pi}_0 \int^{\frac{\pi}{2}}_{\frac{\pi}{4}} \int^{2a}_0 \rho^2 \sin \phi d \rho d \phi d \theta$ but I get the wrong answer (answers say it is $\pi a^3$ .

What is wrong with my integral?

Thanks

EDIT: I think I know the mistake I made. I now end up with the integral $\int^{2\pi}_0 \int^{\frac{\pi}{2}}_{\frac{\pi}{4}} \int^{2a \cos \phi}_0 \rho^2 \sin \phi d \rho d \phi d \theta$ but I still get the wrong answer... I get $\frac{\pi a^3}{3}$ ... are the answers wrong, or...?

EDIT 2: I've solved this problem... I don't need any more help on this. Thanks