How much would it cost to cut one line from a family plan or would it be free?

I have a Verizon IPhone 4 but I'm on a contract with a family plan. If I just cut off my line but keep my family's lines on, would it be free? Or would it cost $200?

My plan is tot cut just my line with T-Mobile and go on a Verizon line without cutting my whole T-Mobile contract because my family will still have their lines with T-Mobile.

It depends, are you still on contract with Verizon? If you are, then it can cost anywhere from $350 to $150. If you aren't on contract with Verizon, your one line can easily leave Verizon and the other lines and the other people on the account will stay on the account.