It's not possible LEGALLY.
There is nothing to "unlock".. It's a CDMA device unlike the GSM counterparts. The MEID is in the provider's library and thus allows them to use or not use it. This phone is not 'locked' to any provider. That's why it's possible to take one w/ a bad ESN and activate it on Cricket or MetroPCS.
Further, there is no "flashing to boost".. boost doesn't use proprietary software that would be available or compatible with the EVO so there is yet another misleading statement. Sprint phones (that are allowed on boost) just work on boost without any flashing or 'unlocking'. If the OP purchased this device this way or paid someone to do something to this device in order to make it happen, my bet is the seller did something illegal. For the record, I'd check the MEID on the sticker inside the phone, compare it to the MEID on the box AND compare it to the MEID that's coded in the software on the device. I'd bet $100 they don't ALL match.
Further, when you attempt to enter the EVO's MEID into the Boost system it returns an error "incompatible plan type" and the system allows the CSR to go no further. This happens whether you attempt to use Boost's Customer service or attempt to go through Sprint's "Back door"..
The OP must have gotten something done to the phone that's illegal for this to happen.
Please see
this thread for reference. I am a moderator over there and I can tell you I delete at least 2 threads a week where people are claiming that they were able to get the EVO on Boost. It's not possible (legally).. absolutely not possible in any way, shape, or form.
IF you'd like your own proof, there are a TON of EVO's on flea-bay for sale. Get the MEID of any (or all) of them and attempt to get them migrated in, swapped in, or whatever approach you'd like to use.
I'll put my first born on the fact that it will not happen. Sprint does not allow it's MVNO's to use the MEID/ESN's from it's "exclusive" devices (Palm pre/pixe, hero, EVO, etc) ..
I hope this helps
--DM1975