Why can't I run Hot Spot and 3g at same time?

[AC Question]

So,my phone has a data plan with its own wifi,and I have a mobile hotspot.I want to use my phone while my daughter uses the hot spot,but when she's connected,my phone won't work.Why?

 

[B. Diddy]

Welcome to Android Central! It should still work. Which phone do you have? Are you using the mobile hotspot that came with the phone, or a 3rd party hotspot app?