Unflash Galaxy S3

[xaephod]

Quicky question. I flashed my Galaxy S3 from Sprint to Boost a while ago. I want to sell the phone, but I need to unflash it. What is the easiest, cheapest, and quickest way. I notice that resetting the phone to factory specs doesn't unflash.

Please advise
Xaephod

 

[Maxime506]

Don't know if this website works:

http/apcmag.com/how-to-unroot-your-galaxy-s3-and-flash-it-back-to-stock-rom.htm

If u could find stock rom, u could make the phone looked unflashed, but according to the website u couldn't get the warranty back anyway.

 

[xaephod]

I am not sure if this is the same thing, but it was flashed to work with Boost. I need to reflash it to work with Sprint again.