International tax agreements

Filed taxes many weeks ago,  but I have an issue.

 

The tax authority of my native country taxed a portion of my employment based retirement benefit earned in that country.   The only tax authority that can tax said benefit is the IRS so, effectively, I got taxed twice on the same retirement benefit!   There is a Tax Agreement between the U.S.A and my native country whose purpose is to avoid this sort of double-taxation.   

 

The tax authority in my native country has requested that I obtain a document from the IRS that clearly states that I am liable to taxes here in the U.S.A since the time that I have lived and paid taxes here.  That document secured, I am to send it to the tax authority of my native country.   That will then insure that I am taxed only once,  by the IRS.

 

For the life of me, I am not able to connect with anyone with the IRS (trying to actually speak to a "live" person) to obtain a document alluded to above.   Also, I wrote a letter almost 2 months ago to the IRS (mailing to an address that is to be used for tax payers of my State, that is Texas) to no avail!

 

Is there either an address for the IRS (International questions) or a more "proper" address that I could use on this?

 

Awaiting helpful information!

 

JJ