If you buy something from someone can they take it back?

So my dad sold me an iphone 5s for $30… & everytime he gets mad he says "i'm gonna take the phone back" & i say "you can't because i bought if from you" & then he says "ill give you your 30 bucks back". Can he do that legally? Because i bought the phone and he does not pay the phone bill

Of course he can do that, you don't own anything unless you are paying your own rent, your own electric, your own food, etc.

If you are a minor, yes he can.

The details are irrelevant. If you are a minor, you own nothing. If you are living under his roof, you have to follow his rules and he can do what he wants. If you do not like it, move out once you reach the age of majority.

Things are different when you're a minor, and he's your parent. It doesn't become fully "normal" until you're 18 and an adult.

In the meantime, he can take the phone from you, and he doesn't even have to give you your money back, especially if he can justify his action as being in your best interests.