A bankruptcy mill is sometimes a derogatory term that's used to describe a higher volume practice, usually a larger firm. They usually specialize in providing the lowest cost possible. One of the advantages for them to be able to make a profit is that they have to also touch the file as least as possible.
That means no return phone calls maybe no personalized attention. As you have to be careful when you're hiring a firm, to go big enough that they know what they're doing and that they've regularly practiced bankruptcy but also not too big that you're not getting your file worked on. Not getting your phone calls answered because bad things can happen if that occurs.