为Driveway的事准备打官司了,但对方不看且退回我certified mail怎么办?！

为Driveway的事准备打官司了,但对方不看且退回我certified mail怎么办?！Wrote and sent the contractor a certified letter reminding him that he had broken his promise however gave him a last chance to finish his job before I resort to a court. .... the contractor returned my certified mail without openning it!_:mad: