Letter 4883C - Verify ID and/or Return Info

I received the subject letter to verify info on my 2024 return. I called the IRS number provided for the 'Taxpayer Protection Program hotline' (800-830-5084) and was advised I needed a previous return with supporting docs in order to proceed. After gathering the required info, I have since called back multiple times over several days, starting the minute the line is open, and cannot get through to an agent. Recorded message says that due to high call volume they are not accepting calls and I should try calling back later or on the next business day, all to no avail. At this point it appears this 'hotline' has gone completely cold is not even being staffed. Any suggestions re alternate means of getting this addressed over the phone? My only other option as far as I am aware is to physically go to an IRS office to meet with an agent, which I would like to avoid if possible.