Wimborne Royal Mail Delivery Office | Sorting Office

I recently ordered something from a private seller who used the Special delivery service, I was contacted over the weekend by the seller who asked if I had yet received my item which I had not.
He proceeded to send me a proof of delivery screen shot from his phone with the order number and the signature and printed name none of which are mine. I was home all day on the day of delivery as I was off work sick and no attempt was made to deliver the parcel to myself. It has now been signed for by someone I don't even know and I still have no parcel! These parcels should not be signed for if they are not delivered to the right address as I am now at a complete loss, money paid for the item gone, and no parcel. No note was left in my letter box to suggest it had been left in the bin or in the shed.

With regret I have given this service a BAD review due to the fact that our postie has AGAIN left a parcel in the wheelie bin...today with a note on an envelope for someone else...not even a red form. This is in spite of my complaint made in person just a few weeks ago.
I cannot think of an easier way to lose important items especially if neighbours put out our bins if we are away.
This is not to mention the parcels left on our doorstep quite often. Nice invitation for a burglar as the house is obviously empty.
Please get this sorted out? I am very happy to collect from the sorting office. RV