How wold be the best way to sell a iPhone?

I have a iPhone 4 16gb that I brought a few days ago.
Thinking it was a good price when I brought it but now i've just relised that it's costing me more then there worth!

I paid ($430.00 including delivery)
No I've just realizing there not worth an more then $300 tops,

Don't care if I don't get my money back just want it gone as I've got to stoping buying things,

Anyway I can sell/swap it quick and fast?

I know I'm an idiot, should done research before I brought it

It's just a hundred and thirty dollars, hustle

I dropped my local phone service and just use cell, they are worth it imo.