[Anker]

I am going to be a bit cruel here. You need to control yourself. You asked them to fix a problem and they addressed it by performing the work that most probably would fix it, and you agreed to have them do it. Unfortunately suspension noises are notoriously difficult to fix unless there is a glaring issue that shows where it is. The fact that it is still there simply means that the work they did didn't include where the problem is. Neither they nor you could know that up front. You say they were "confident" they knew where the problem was. That's kind of vague and not certainty.

I think its fair to ask them how they plan to proceed and point out that they have already made money on work that didn't fix the problem, and if they are the kind of people I like to work with they will give you a break on further work.

You should also recognize that the work they already have done will eliminate suspension problems that are bound to crop up sometime in the future, so you have received value for the work you have paid for.

So go and have a mature discussion with them about how to proceed, and don't be obnoxious.

If they become obnoxious, walk and find another mechanic.