Different carriers have different policies. At Sprint, with little or no credit history you'd probably have a $125-$150 deposit, but you'd also have a spending limit. After 13 months of on-time payments your deposit would be refunded (actually, applied to your account balance), and your "credit reevaluated, which could mean a higher spending limit or no limit at all. You'd be shocked how many customers still have that limit after three years, but you'd then understand why the need for a deposit exists.
How long will V keep your deposit?