How Do I Deal With Poor Warranty Service?

On 12-10-10 I purchased a microwave (serial # TR 0 2148753, model WMH2175XVB-2) al LOWE'S in Cookeville, Tennessee.  It stopped working the week of 7-18-11.  If you turn it on it runs and acts like it is working properly but it will not heat.On 7-25-11 I called 800-253-1301 and told the person who answered the situation.  She told me the warranty had expired a few days before I called because the microwave had been purchased in July of 2010.  I have the receipt indicatin otherwise.  The date of purchase was 12-8-10.  So she told me she would schedule a service call, which she did, and I should just show the repairman the receipt. I made arrangements to be home the morning of the appointment, but the repairman did not come.  The repairman called and rescheduled for the following day.  The repairman did arrive within the two hour window, opened the door of the microwave and looked inside and said I know without taking it apart what is wrong with it, but I will have to order the part.  I never heard from him again, and apparently neither did the person who handles your calls.  I found out later he did order the part, and he did receive the part, but he was no longer working for you.  I called again and another repair service was contacted for me.  I again waited for their call to schedule an appointment.  The call never came.  I went back to LOWE'S and explained the situation an was told they could not help me because I did not purchase a LOWE'S warranty.My microwave is under warranty and has been useless for over ten weeks.  Do I have any other options other than contacting the Better Business Bureau?