ST Couriers — deliver to wrong person

I am Ponnusamy working at Taluk office Namakkal .My brother in law had sent a doccument on 10th Dec through ST Couriers with clear address and my two mobile numbers on the cover.After two days I asked my brother in law to enquire about the cover.After contacting the booking office he told me the cover was delivered and he gave me the number of office in charge at destination office.I contact the office in charge and I was informed that on being door locked the delivery staff delivered it to neibour and mention a name. I replied him no such person around my house and asked him to call back after recovering the cover.The next day he inform me that he had sent his staff to collect the cover.After some time the staff came on line and told me that the cover was dropped in the mail box at at my house gate.I asked him just bring it to office and I will come there.then he inform me the letter was with office. I asked him to deliver to me at taluk office .They simply told we cant and redirect to sender.I want to know the condition of cover wheather tampered?And what happens if its a time bound doccument?Isn't it a paid service?
Thankyou.