Hi:
You didn't indicate who your carrier is. If AT&T/Cingular, you could take a look
here. I AM NOT ENDORSING THEM AND I HAVE NO EXPERIENCE WITH THEM. So do your due diligence and make sure they can provide the service you want. They do have a 99+% positive feedback.
Or
this vendor claims to be able to do any Centro on any network. Again, same cautions as above.
I found these through Google....the information is out there.
Of course you could also look to eBay for a good price on an unlocked Centro. I am not sure what they are selling for.
I thought there was some kind of a rule they had to give the unlock code if requested. That could be GSM and you may have to be an established customer for some time. Not at all sure about CDMA services.
Good luck and let us know how you make out....
SteveTaz