[cisco-voip] Local Number Portability in the United States - can a carrier "lock in" DIDs?

[Robert Kulagowski]

If I port DIDs to a carrier, and then change my mind, is anyone aware
of difficulties in porting out numbers? Has anyone run into an issue
with a carrier preventing DIDs from moving?

I'm not talking about slamming - so assuming I've done an "unlock" on
my DID, should there be any problems?

Thanks?