為Driveway的事準備打官司了,但對方不看且退回我certified mail怎麽辦?！

為Driveway的事準備打官司了,但對方不看且退回我certified mail怎麽辦?！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: