Need Help Getting a Sprint tp flashed to Alltel back to Sprint

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Thanks in advance for any tips. Long story short. I bought a Sprint Tp off Ebay. Seller said it was flashed to Alltel then back to Sprint stock. I had it activated on my wifes Sero but I get a Verizon prerecorded message when dialing out. So the seller obviously did not flash back or adjust the settings properly. I found a thread around about going from Sprint to Alltel, but how in the world do I go back to Sprint. Frankly I wouldnt even know what to look for in terms of software/settings etc. I have tried Flashing back to Hermann Sprint Stock as well as other custom roms but they did not do anything as I still get the Verizon prerecorded message. Are there any particular settings I need to modify? Btw the seller is being a tool and I like to keep the phone so returning it is my last recourse. Good Karma to anyone who can help