Non linear regression calculator

Are there any really good non linear regression calculators around the web? Or is something like MATLAB the best solution?

I tried using excel and its solver tool, but it's complete garbage lol. Granted, my modeling formula could be better, but there's got to be something better out there.

I used the model equation: $\mathrm{value}(t) = Ae^{-bt}\cos((\omega)(t)+(\varphi)) + y\text{-intercept} + m(t)$, where $m$ is a slope used in attempt to match the shape of this graph

Here's what I got from excel

Any ideas what tool I can use for a more accurate regression?

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