Please clarify. You indicated that you asked for "validation" by way of letter to the CRA. If what you sent was labeled as a DV letter, they probably trashed it. The CRAs have NO part in the DV process. That is done strictly between you and the CA. You cannot DV an OC or a CRA.
Can you clairify what you sent?
Robert's note above is absolutely correct in that you should not be trying to validate a debt with a CRA. The only thing you really do with the CRAs themselves is dispute information found in your report. They will in turn ask the reporting organization to verify the debt.
Regarding the address... the one that is used in Experian's online dispute system is not what you mention. They list:
PO Box 9701
Allen, TX 75013
Hope that helps!