Early Termination Sprint and being asked to return device

Okay so I've had tons of problems with sprint including dropped calls and blocked calls and horrible data speeds and they've said that I can cancel my contract, they won't charge me anything except what I owe for the current month and to mail them back my iPhone 5… To me that's laughable, I paid $199 plus the full amount of tax for the original $699 price because I live in CA so it came out to about $260 for the device. And they expect me to just take that $260 as a loss and send them back my iPhone that's just ridiculous, is there any law that would bar them from requesting that I give the device back? Or at least get my $260 back if I do give them the device back?

I mean I did nothing wrong, they provided horrible service, and I compared it to other Sprint customers and it was terrible in comparison, I had to replace my iPhone 5 SEVEN TIMES, so Yeah it's something on sprint's end which is why they said I can cancel if I want.

Ok, so in fact, there's no law forcing you to give them the phone. Cell retailers often will try to get you to give back your phone because it makes them a large amount of money. An iphone can be sold on ebay for as much as 800$. You should deny them the phone back simply because you do not have to give it to them. The phone is now your possession, not sprint's. This is not affected by you terminatig your contract early.