Lose Power Steering problems of the 2000 Mercedes Benz M Class

A year ago I was turning a corner in my mercedes ml320 when the steering wheel "locked. " it had lost the power steering fluid and for me, the wheel was impossible to turn. I was told there was a problem with the clamp. It was under warrenty and repaired at simonson mercedes, 1626 wilshire blvd, santa monica , CA 90403. One month and one thousand miles later the same thing happened. This time I was told that mercedes had sent a modified clamp to correct a problem with the origional hose clamp. April 20, 2003, at 30,000 miles the power steering failed again. I had it towed into simonson on April 21, 2003 and have refused to pick it up even though it has been "repaired. " I told the manager that I felt this was a life threatening defect that they had not been able to fix twice in the past. I asked them to buy back the vehicle and was told someone from mercedes higher up would contact me.