I am a 20 year old college student and my parents takes my cell phone away when I need to study for a test for school because my grades aren’t that great and I procrastinate. My parents pay for my cell phone. Is it wrong of them to take away my cell phone away when I am an adult because I have to study?
Nope. Their money, their rules. Pay for it yourself if you want unlimited access.
I am a teenager (not a parent XD) and I have to agree with @intparent … The phone is essentially their property, so they can really do whatever they want with it.
If you want them to pay for your phone, show that you’re responsible enough by getting better grades. 
You’ve been worried about being perceived as an independent adult for a while now, according to your post history… I think people gave you similar advice when you asked about a car? Have you made steps to get rid of this anxiety, like starting to pay for some things yourself?
Well, they could just say, if you don’t maintain a 3.0 we’re done paying…I think its wrong for them to keep enabling you. If at 20 years old you have to have your phone taken away so you will study, there’s bigger problems lol.
Yes. I have paid for my clothes, makeup and food on my own but the rest, my parents pay for. I don’t have my own car yet.
I wouldn’t say it’s wrong, but it seems unnecessarily strict. But if they pay for it …
Based on your other threads, you seem to have reliability/accountability issues: cannot deliver customer service on time, cannot study w/o supervision, cannot be trusted (anxiety attacks) to safely operate a vehicle.
Have you considered mental evaluation? Could you possibly have a slow processing speed disability?
As a parent, my philosophy is I will leave you alone and you can study however you want IF IT IS WORKING.
If phones/computers/TV is distracting you to the point you are not doing work and it is affecting your grades, you are darn right I will get involved.