I was very happy to see that I qualify for USPS Commercial Plus pricing since I shipped over 5000 flat-rate envelopes in 2013:
"Commercial Plus prices are available to Priority Mail (including Critical Mail) customers who qualify for Commercial Base prices and whose cumulative account volume exceeds a combined total of 5,000 letter-size and flat-size pieces (including Flat Rate Envelopes, but not the Padded Flat Rate Envelope) or 75,000 total pieces in the previous calendar year (except Priority Mail Open and Distribute) or who have a customer commitment agreement with USPS"
I called my local USPS Business Service Network location. The saleswoman I was eventually transferred to has insisted that I sign a customer commitment agreement to ship a certain volume before she will move my request forward. I emailed all of the above to her but she refuses to budge without any explanation for the contradiction.
Call Washington DC - I did this once when a local postal person was breaking the national rules. I do this all the time when lower level people refuse to help. Stop wasting time with this person...if you think you are right - I have no idea if you are...