Unfortunately there is no way to change the ESN without some special hardware/software that usually only the people that make the phone possess.

man i got taken on htc sprint evo,paid 200 dollars and it was claimed lost.I spoke to the owner and offered it back to them,but they will not meet me to get the phone back. I'm not even asking for any of my money back just trying to be nice.I'm starting to think they were in on scaming me,.