Speaking rear breaks S-Type Sedan

Anyone had problems with rear breaks squeaking after replacement. I've had my breaks redone four times, started with the basic change, inspection and still noise when breaking, its like a loud annoying squeak, took car back in they replaced everything, no noise for a day or two then it started again, went back in, replaced and manufacturer replaced for free, still squeaking but this time when breaking at 50mph, and just light tapping and 30mph noise is off and on. Not a happy lady so I went back in, they put the best of the best on the whole shabang thought it was fixed two days later the squeaking is back. I know I'm not breaking hard, just average breaking when coming to lights or exit hwy, so at a list for what the hell is going on. I even video taped speed odometer to show machanic when the sound comes in and how I was breaking no problem on my end. So once again replaced,, guy said a spring pin can out possibly by hitting a pothole??? Hmm long story short the speaking is back I dint know what's going on and machinic is at a list, btw he works exclusively on Jags and range rovers. Great guy just worse problem with breaks, any ideas?? Quite embarrassing to pull up in a beautiful car with noise. I don't enjoy driving my Fancy right about now. Help!!