Orders I have received from Signs365 have been nothing short of perfect. The colors are always as I had intended them
Now granted, my monitor is calibrated to the point of what I am looking at is what should print. Also, I KNOW my colors. By this I mean over time I have learned what CMYK values I need for the output to be EXACTLY what I want even if I am unsure about how they are viewed on the monitor.
If your monitor shows a hot pink color when displaying 100% Magenta, it's probably not calibrated properly...it should be darker than that. If your monitor displays a robins egg blue color when viewing a 100% Cyan, then yes, your calibration is woefully off.
Given my experience, both submitting art to be printed, and accepting files from other to be printed, I have to agree with some earlier posts that it's a good bet your files could contain colors that differ from what you intended them to be.