Welter Construction / Failure to complete work

We suffered a hail storm in April 2014 and hired Welter Construction to repair roof in May. We also contracted to have windows and siding replaced. They promised to have work completed by middle of July. We finally got a roof two months later, but they did not even start the windows and siding until December under threat of legal action. Welter Const. signed a contract guaranteeing the work to be completed by January 1st, 2015. It is now the middle of January and we have a broken window that we have been waiting for 3 months from them to replace, our bay window that was the number two item for replacement has not been touched, and the siding in not done and nothing was chocked. We had heard nothing from Welter Construction in over a month.