I'm not sure exactly what you can do about it, as far as getting them to do competent work. Complain, and complain loudly, but in the end, realize that they might not have the expertise to be able to fix everything correctly.
However, I hope you use this as motivation to find a real mechanic. Get on Yelp or use your Google-fu and find a local shop that will communicate clearly with you and take pride in their work. All of those chain shops, Pep Boys, Midas, Firestone, Aamco, etc., all of them are terrible places to take your car. They prey on the uninformed, charge high prices, and usually combine that with poor workmanship.
