Our landlord has not fixed the heat after 4 months of the heat not working properly. I?

She sends a tech out after we have called and emailed her for no less than a week. The tech "patches" the problem, leaves and the heat goes out within a few hours again. This last time, she has taken 16 days to send someone out. She brought 2 small electric heaters for a 2260 sq ft house. We are tired of our 10 yr old being sick due to the lack of proper heat and we want to vacate the premises. Our lease for one year and we have been here for 7 months. This is not the only problem with this house, the septic tank backs up constantly, however, the heat is the biggest problem! Any advice or help is greatly appreciated.