US Post Office

I sent a certified letter too my landlord at his p.o. box with this company for my rent.The mail box company sign for my mail and lost my rent.I called and talk with the manager he didn't have time to talk told him what happened he said he would get back with me here it almost a month later and nothing from this company. I am holding them liable for my rent late fees stop payment. Or just return what your company sign for. Charlene W.