St Courier — I'm complaining about delivery

I went to St couriers Kumbakonam to receive a parcel that was to my sister. I showed the courier number to them. Ther checked and told me " there is no parcel in this number". But they called the day before yesterday and yesterday to collect the courier. If there is no parcel, How did they call? And after a while, they told that they have returned that. How could they return without any information? This is very bad service. And I'm very sorry to say this " you are doing a worst service in courier. Very worst. There are no words to scold you. Because you did that much of service.