Mitsubishi Air Conditioner Cooling Issues and Neglectful Service

My recent purchase of a multi-split air conditioner that fails to provide cooling has disappointed me. A service technician came around 20 days ago but couldn't find the problem and left. There has been no follow-up or communication since then. I contacted customer service last week to explain the situation and created a service request, but there has been no response. My home has four Mitsubishi Electric air conditioners, and while my older units work perfectly, the new ones refuse to cool. The technician who arrived 20 days ago didn't understand the problem and even attempted to determine cooling by touch. This experience has shaken my faith in the company. For their service and commitment to their products, including replacements if necessary, I chose a reputable brand like Mitsubishi Electric. Mitsubishi Electric, sadly, has let me down. I'm forced to use a portable cooler to cool my living room, which reflects poorly on Mitsubishi Electric.