My parents are not ready to keep my dog because he is not trained.What to do please suggest?

I am Justin from Dindigul . I have GSD dog (crossed ) 18 months old . my dog not trained . so if I say sit , stand , come. dog not obey my order . Full out of my control. some times my dog suddenly escaped and go to other homes and roads badly. My parents are not ready to keep my dog because of he do not obey. I need my dog obeying. so please any one help me and what i do and don't do ..