I bought a iPhone 5s with a clean esn from Sprint but they won't unlock it.....what can I do? I'm with Verizon and I refuse to buy another phone!!

Firstly, why did you buy a Sprint locked phone if you are with Verizon? Only a Verizon phone will work with Verizon.

If Sprint won't unlock the phone, then there is absolutely nothing that you can do. Return the phone to where you purchased for a refund because if Sprint refuse to unlock the phone for you, there is nothing you can do and you will never be able to use this phone so you will effectively have a brick.

If Sprint won't unlock the phone and if you don't have a contract with them, then it is entirely their choice whether they help you or not, either return the phone for a refund or sell it to someone who uses Sprint and can use the phone. If you are with Verizon, then you need to buy a Verizon phone - Verizon is a CDMA carrier.