Mechanic screwed my car and now unable to fix

I had a mechanic replace my brakes and struts the same day.Ever since he had replaced my brakes and calipers, there's a wierd echo-like sound once i start to hit my brakes.He said it should go away but didn't.It even makes that sound on turns as well.I never had this issue before he serviced my car.I had gone back to him3 times and the 3rd time he claimed that he had put the brakes in backwards and now he put them the correct way and the noise should go away.It didnn't.So now I turn to you guys.Can anyone help my slow mechanic by suggesting what might he have done wrong while servicing my car that would make that sound kick in when I start to hit my brakes or turn?BTW...He suggested that it could be the rotors but that wasn't it as the sound still occurs after replacing them.Could it be cheap brakes?

1996 nissan maxima.

...there's a wierd echo-like sound once i start to hit my brakes...

If the noise can be repeated, make a tst drive with him so he knows which corner the noise comes from. This way you can both agree about the noise existence and the successful repair (if). He should be able to correct - free. If not, try another shop: some repairmen can do just so much, outsider pushing wont help raise iq... (He is right in some aspect: Often brakes are noisy after pad swap and do settle during first 1k miles - needs patience but cause also has to be known/verified.)

There are multiple reasons from rims to worn calipers and/or guide pins which may exhibit their age after pad replacement. Have calipers (?) truly been changed ... I never trust what is said; check out yourself or go, verify this in another shop; sometimes :( u just pay ... What is the mileage = why would they change the caliper$?

If u happen to have new calipers, then the noisy one new caliper could be bad, only replacement helps ... there must be some warranty.

After strut replacement there should be toe-in, camber/caster wheel alignment. Wheel bearings should be checked.

You have the bill: pls list all parts changed - then its better to evaluate what has happened.

If the noise can be repeated, make a tst drive with him so he knows which corner the noise comes from. This way you can both agree about the noise existence and the successful repair (if). He should be able to correct - free. If not, try another shop: some repairmen can do just so much, outsider pushing wont help raise iq... (He is right in some aspect: Often brakes are noisy after pad swap and do settle during first 1k miles - needs patience but cause also has to be known/verified.)

There are multiple reasons from rims to worn calipers and/or guide pins which may exhibit their age after pad replacement. Have calipers (?) truly been changed ... I never trust what is said; check out yourself or go, verify this in another shop; sometimes :( u just pay ... What is the mileage = why would they change the caliper$?

If u happen to have new calipers, then the noisy one new caliper could be bad, only replacement helps ... there must be some warranty.

After strut replacement there should be toe-in, camber/caster wheel alignment. Wheel bearings should be checked.

You have the bill: pls list all parts changed - then its better to evaluate what has happened.

Well here's what ticks me off.When I go test drive the car with the mechanic,the noise didn't come in.I went twice and twice it failed.I can't really understand when it and why it makes that noise.As for the calipers,he says he don't think that could be it.Calipers were replaced because the mechanic broke the originals when removing them(claims they were rusty and old)so I got charged for the new ones.BTW...I've probably driven more then 5000 miles ever since these repairs so the brakes must be settled by now so that cant be it.
As for the parts..he never listed what the brand of the brakes are on the reciept just listed what work was performed.Here's what he listed:
Shocks monroe matic,shocks frant,
shocks rear sensa-trac,front brake job,front brake pads,service rotors,rear brakes,caliper replace right and left side.
The big issue is i'm trying to sell my car and that noise is scaring customers away.

...Shocks monroe matic,shocks frant, shocks rear sensa-trac,front brake job,front brake pads,service rotors,rear brakes,caliper replace right and left side...

From the list one may get a pic that only front pads were changed, calipers are still the original. Then rear calipers have been changed...(?).

If so, he did not know that at rear the pistons have to be turned when they are retracted - to fit new pads. I guess (?) the hbrake system adj screw inside the rear caliper was destroyed by him... wouldn't be the first case. (Eh I was stupid but lucky) Check http://www.cardomain.com/ride/748507/18

Does the sound vanish [only] when two ppl sit in the car [add more weight = ride height changes]? Then the issue might be a worn wheel support bushing(s) and/or strut bearing(s). This is why I asked the mileage... (?) Note that new struts are much more solid and the resistance they cause can 'bring new issues' in the view.

Anyways it may be impossible to repair if one cannot repeat the noise - if no loose bushings can be found.