Don't buy Dell

I did a lot of research before finally deciding to buy a Dell E 5450 laptop. This is by no means an entry level machine and is rated quite highly for business use. I have used Dell before and was impressed by its reliability. This machine however is faulty. The screen goes blank intermittently. At times It goes blank every 5 minutes and other times occasionally. Each time it goes blank it takes about 3 minutes to restart, luckily work is not lost. I reported the issue to the call centre in Bangalore. I have been ordered to try many different tests in bios mode safe mode, plugging in different monitors etc. after about 20 e mails and 4 weeks later a technician was sent to replace the motherboard. The technician did not install the battery correctly and did not clip the keyboard cover on correctly so he had to come back, this on its own was shocking service. Replacing the motherboard did not solve the problem and it seems that the screen goes blank more often than ever before. Every time I complain they ask me to perform more test, what happened to NEXT DAY ONSITE WARRANTY. I want a machine that works, either repair, replace or refund me.