Originally Posted by HACKhalo2
(device not supported, esn not valid, etc)
This type of response tells me that the reason it won't activate is because they will not allow a Sprint phone on their network. Period.
If you can activate T-Mobile phones under your unlimited plan then personally I would try to sell these phones (see Ting info below) for near what you paid and get a T-Mobile compatible S II or better on your plan. CM 10.1 works well on the Epic 4G but occasionally it can be a little pokey sometimes and memory is tight. Also you still need to boot into Samsung Gingerbread FC09 to activate, etc., see link below. It may be a selling point to flash these phones to CM 10.1 (definitely enable the ability to boot into FC09 as mentioned below).
Otherwise if you insist on using these this is probably your only option:
If you're lucky find a cheap Samsung Galaxy S (same as Epic 4G) that will run on Metro PCS and either use it, or if its broken, try to migrate its ESN/MSEID to the Sprint Epic 4G. I don't know how this is done, but I have read this is the way you can get competing carrier phones onto competing networks. This should allow you to activate the phone. How well it will work considering MetroPCS is ditching CDMA is just a guess.
I was going to suggest some options involving a MetroPCS hotspot, but then I thought that might not qualify under your unlimited plan?
Regarding selling them:
If you know anyone who has decent Sprint coverage and barely uses data, but still wants to use a smartphone over WiFi then convince them to buy your phone and sign-up with Ting (http://www.ting.com
). Give them $25 credit with my link: https://z25ms41o9h2.ting.com/
Dual-boot from CM 10.1 into Samsung Gingerbread FC09 for PRL, Profile, Activation, Sensor Calibration: