This totally depends on how much time you want to put into selling your phone and what type of protection you're seeking for in the sales process.

Selling your cell phone at a store is the easier, faster way to go with but chances of getting a desirable amount of your Smartphone are lesser than an online website. But, if you need the money in a pinch or you’re eager to upgrade, an instant off-line store is a good option.

On the other hand, selling to an online website might allow you to pocket more money. Moreover, an online website provides numerous features such as faster payouts, real-time tracking of your sale and proper customer support. 

If you have no clue about the trustworthy websites, then you can sell your phone on any of these websites:

•       Gizelle

•       Recell Cellular

•       Swappa

•       Recycle Device

•       uSell