Can I replace a lost iPhone 5S?

I lost my iPhone 5S, with a T-Mobile service. I purchased it unlocked. I also don't know if I have coverage on it or not. Can I buy a new one at Apple for a low price, or do I have to spend $800 again for a new 5S?

It's gonna cost you at least 500 for a new one. You can find that deal on ebay just make sure it's from a trustworthy seller