What can I do if a USPS carrier forged my signature?

My package was lost but the carrier said he delivered it to me and received my signature. I called USPS to file a claim and they stated that the carrier didn't get a signature, the a week later I called again they stated to me that the carried said that he knocked on my door and I signed for the package. Few days later I called and talked to the city manager and he stated that he called the carrier and he said that I was sitting on the porch when he delivered the packaged and I signed. I am getting two different lies. After I kept calling about a week later now my signature showed up which I didn't sign.