I have been flying for work and using my personnel phone. Does the phantom 4 use my phone data and at what rate is the data use
if I am filming?

You can fly without using any data at all.
Like half the flyers out there, I fly with a wifi only tablet and have all the features anyone else has.

I don't know how it is now, but in the past the phone app was sending all sorts of data back to DJI servers in China, I would disable cellular data while you are flying the aircraft to prevent it. As Labroides says, it is not necessary when flying.