Did not receive the delivery as we were away on vacation, but I must pay???

I placed an order with them on the 16th December and asked if it will be here before Christmas, I was told they take 10-14 days for delivery, I then notified them that I will be on Holiday and are going away to the Freestate and will only be back in January, then I got a n SMS on the 28th of December while in the Freestate that my parcel was delivered, well I found that very strange seeing that I was not even close to Gauteng, I queried this with the delivery company who told me it was delivered on the 28th December and was signed for by a Samsert my gosh I do not know any person with that name, no one in our complex is named Samsert!!!- I called a few times, I sent email after email, but still n response, now received my statement and I must pay for something that I did not signed for as me and my family was not even at HOME