Good morning Bernie,
First, please don't respond to lenders who initiate unsolicited contact with you. There is no guaranty that they are approved to do business, and you have no way of knowing if they are offering a decent deal or not.
By completing a form such as the one on our site, you at least know that the lenders are licensed and you can easily compare their offers to other competing providers, allowing you to choose a better deal.
That said, not all mortgage lenders have USDA loan approval, and not all loan officers have the training to originate these loans. In fact, you can refinance a USDA loan to a conventional (non-government) loan with almost any lender.
You can refinance to a new USDA loan (streamline) with the right approved lender. I assume that you are trying to refinance to a new USDA mortgage.
However, if you have enough home equity and a high enough credit score to refinance out of the USDA program, consider doing so. There are conventional programs that may be less expensive in the long run. If that's the case, please get back to me and let me know what your home value / loan balance is and give me an estimation of your credit, and I'll do my best to point you to another program.
If, however, you need to streamline from a USDA to a new USDA loan, you'll need a lender able and willing to do this. The USDA maintains a list of approved lenders here. https://www.rd.usda.gov/files/SFHGLDApprovedLenders.pdf
Good luck with your search, and please get back to us here if you need more help. Thank you for writing and good luck.