Coffee machine under guarantee

Our DeLonghi Coffee Machine is under extended guarantee from the supplier and is now in for repairs for the fourth time! It is obvious from the fact that it is returned without the problem fixed that the company doing the repairs cannot fix it, yet we have received nothing but excuses and promises. If the machine cannot be fixed it should be replaced by Dion Wired. But the store manager ignores messages left for him to contact us and hasn't gotten back to us in 1 and a half weeks. This should be unacceptable in any industry! The people in the store blame Dion Wired head office, but fixing this problem is ultimately their responsibility. The machine is under guarantee and should be replaced if it cannot be fixed - this shouldn't take months to sort out.