Just to make sure...

[Super Buu]

Grand Kai looks very old, and everyone has a lot respect for him and his training skills. The fact is, is that he has been lazy and his skills have degraded in millennia of time. Though, he lets fighters in Heaven train and fight on his planet. He also can call Baba or one of the other witches for help. Meaning people in Heaven can pay for the witches Rituals. Just switch Universe and Next Dimension with each other in the description.

So yup, if you go to Heaven, you can pay for a revival. But no, you can't call her from Yemma's office, unless staff says otherwise (which they probably won't).