Has anyone had a client(s) who have successfully reached the IRS by phone - either the Taxpayer Advocate's office or the number on the 5701C notice?

I have a client who has been trying to resolve their 5701C notice since April.

They entered all of the requested information online, and then were instructed to call a particular number.

And as many of you know, there is no answer or opportunity to leave a message.

There are 2 Taxpayer Advocate offices near them, but neither of them can be reached either.

Has anyone out there had any luck getting their clients through this mess?

Thanks in advance,

John