Victor,
Talk to your tech support person for MCI. You may not have been made
authoritative for your segment of the block of addressing, even if you are
the DNS of record for the domain. If your upstream does not make you the
source of authority, then they still are.
It happened to me, changes to DNS were not seen by people outside our
network. Our upstream was still authoritative for the address segment.
David Payer
OMNI Internet
www.ia-omni.com