I work in banking. I cannot think of any bank that will refinance you into a better rate when the amount owed is more than the market value of the home. Many banks are even loathe to lend at anything >89% loan-to-value. BTW -- Jumbo mortgages can only be done at <60% loan-to-value.
I think what you are trying to get into is a loan modification program. Unfortunately, you are usually not eligible for this until the loan is at-risk of default. But because you are making payments on time and in full, your bank feels your current terms are just fine with them.