How to use verizon iphone on sprint network?

My iphone 5 recently crashed the other week and I've been using my dad's old phone which has a ton of problems on it already. For my birthday my friend offered me his old iphone 4 that he's not using since he upgraded to the iphone 5s so I'm wondering if I can use it on sprint. I took it to the sprint store and they told me I need to have it flashed or else they won't be able to connect to it and from what I've gathered online I have to have my friend contact Verizon to unlock the phone. Basically I'm just wondering will they unlock it for him or should I stop pursuing this.

Ask tmobile

If you get Sprint to activate a Verizon device it will be a miracle.

Sprint will not activate a Verizon device and vice versa.

Unlocking a CDMA international device has no benefit in the US.

International CDMA devices are for use on GSM networks outside of the US only.

You have to contact Verizon to unlock it for you.