I started having problems with my G3 portable unit in late January. I contacted LPT and although their technician made no attempt to troubleshoot problem over the phone, or even ask what the display read, she said it was " the column ' and would cost 300 $ to repair. Although the unit was under warranty for nearly another year, she said that " columns: were excluded. We sent the unit overnight UPS on Feb1. They said they would call and tell me what was wrong with it and how much to repair. I called a week after it was received and they said it had not even been looked at. Eventually they sent a unit to the wrong state TWICE. They sent units that did not work TWICE. My many calls and emails usually were not returned. I had to call repeatedly to get any response and then they would tell me there was nothing wrong with the it. This is a necessary life saving piece of equipment that I was without for nearly 3 months due to the worst customer service I have ever experienced. I finally gave up and sent the still malfunctioning unit directly to Inogen. I am spending 450$ to get a refurbished unit from them because LPT would not repair it. TERRIBLE SERVICE