I never have chromogenic film printed at a mini lab. As mentioned, the paper is color paper and most of the labs don't bothere to use a grayscale channel.
I take my film to the drugstore lab and ask that they develop the film and can the images to a CD in TIFF format. TIFF is important here or else you'll get tiny file sizes. Even then, the images will be in a color channel, so when I download them from the CD, and process them in Photoshop, I convert the image to grayscale (image>mode>grayscale). I then go to (image>adjust>levels) and adjust each level (black, gray and white) until I get what I want.
Other image processing programs may work differently.
However, YOU did nothing wrong. It's like working in a wet darkroom. YOU have control over your images and their quality when doing digital imaging.
Enjoy the experience.