ok so i have an iphone 4 8gb. I had it for about a year and there r hardly any scratches. The new samsung galaxy S4 just came out and i really want it. I'm with a $25 a month plan and i want to keep that plan. How much do you think i will get for the iphone if i trade it in a koodo so i can use that money to buy the samsung? How can i do it? Can i keep the same plan and number? Thx!!!