Inconsistancy and Call center that doesn't answer

I was supposed to receive a parcel from UNISA and wasn't at work when the delivery was made. I saw on the tracking number that it was returned because I wasn't there to sign. Last week another parcel was delivered that was signed for by the receptionist, therefore I assumed today that the same will happen but it was returned.<br> <br> I phoned the 24 hour call center to try and sort it out. Of the 11 times I phoned, I got through to one person who then transferred me and the phone got cut. After that, every time I phone, the phone was picked up and immediately put down without talking to me. <br> <br> I just want to make arrangements to have the parcel delivered again and I would like to find out why the delivery guys sometimes let other people sign for a parcel and other time not.