Which address should be used?

If you have any idea which one of them is contacting you (which you should), I'd send it to that particular one. Otherwise, yes, just go with whoever's closest, as long as you're sure that location is part of the same "network" that's trying to collect on the account. And, as always: certified mail, return receipt. :D

I would use the one where you account is located at.

If you have any correspondaces from them then I would use whatever address is listed there

I really don't know which office it is.The few times I did talk to them I told them the account they're trying to collect on has agreed to be part of the consumer help program we are in,here's their number,you should call them.That's not what they want to hear and they hang up.My own dumb fault for not asking for their address.Shucks I'll have to answer the next call to get that.Oh well,they call all day long so it shouldn't be much of a problem.Thanks for the replys.

Do you have a copy of the signed agreement from the origional creditor which your counseling agent should have forwarded to you. You should also forward a copy of that to the agency.

Creditors have been known to send those accounts to collections agency by accident. It's a quick fixed as long as you have a signed proposal from them.