Monro Muffler Brake review: Service done on my car

Replaced spark plugs loosened bolts on high pressure fuel pump and never tightened properly bolts broke after a day or so of driving had car towed back to them they said they would drill out and replace they took pump off to do this and there is a process to do this as im sure they didn't do because they thought it was a egr valve and not a fuel pump I had to explain this to them but they drilled the bolts out replaced with two different size bolts I went to pick up my car they told me my car wouldn't run past 3 000 rpms and my cat was plugged had car towed to another shop they told me cat was not plugged so apparently by what monro did with the pump the tension spring on the pump damaged my cam shaft why are they working on things if they don't know what they are doing I will be pursuing this legally