Cingular Too Verizon?

Ight so.... I have Cingular. We Have A Family Plan with Me My Mom, My Dad, && MY Sis On It Ok? I was Wondering if There Is Any Way That I Could Just Switch My Phone To Verizon. Like Keep All Theres On Cingular But Switch Mine Verizon. You Know. Cuz They Dont Care But i Want Unlimited Texting && A White Chocolate Phone But The Thing Is That i Dont Have An Arm && A Leg To Give Up For This, So Bottom Line Is, I Wanna Switch One Number From a Cingular Fanily Plan Too A Verizon Plan with Unlimited Texting && a White Chocolate, Without Paying An Arm && A Leg. So Does Anybody Know If This Is Even Possible? && Could Someone Give Me Like a Close Dollar Amount?