All orders must be signed for?

Hello,

I sent a tracked parcel that Royal Mail claimed was delivered, but the buyer insisted they did not receive it and got the money back. I understand that I was a fool and should have paid a bit extra for a signature. The A - Z claim was denied saying that proof of delivery does not constitute proof of delivery.

My question is, what happens if somebody says that they didn’t sign for it, and it is someone else’s handwriting? I must remember to do that with all parcels I receive so that I can get a refund.

David