Shocking Samsung service

My folks are having endless problems with their Samsung microwave (might I add … the second one) It makes a loud grounding sound when in use My dad , who is 82 years old has taken it down to the store twice, as it’s still under warranty The first time it took almost 6 weeks before they got it back No loan machine was offered , I had to beg for one When they eventually got the machine back , I was the first one to use it , and it was making the exact same noise …loud grinding sound ….almost like a concrete mixer My dad had to take it back to the store again. He insisted that the lady in the repairs department turned it on so that she can hear the loud grinding sound She turned it on , and heard the grinding sound! Again she booked it in for collection by Samsung To date they still haven’t got their microwave back. My dad called the store this morning , and the lady at the repairs department said that Samsung responded and said there is nothing wrong with the machine I’ve had enough of this **** service. They con you with a 10 year guarantee sticker on the door …which by the way only covers the inner casing of the microwave Nobody answers the phone at Samsung, so you left to deal with the repairs depart at the store , and get absolutely nowhere!!!!!! I cannot believe that a brand like Samsung can provide ( or not) such pathetic service Absolutely disgusting!!!!!!