How do I get through the phone system at the IRS and actually talk to someone?

I sent in my tax return via certified mail and have the receipt and confirnation that my taxes were received. I also have the IRS notices that payments were received and also have credit card statements that back that up, but the IRS has sent me a letter stating they do not have anything and their phone system is so convoluted that I don't know how to actually talk to anyone. HELP