That phone will only be any good now as a paper weight.
The IMEI is blocked from paging all networks so even an unlock wont cure it- as used to be the case.
THe phone will be very much stolen.
Sorry to break it to you- anyone offering to change the IMEI is likely to have the morals of a people trafficer as it is seriously bad show and if caught will be sent down for 5 years.
Jake