my grandson bought a phone from you (not cheap) it was delivered last Thursday and signed by a Amy,

[gillsmith]

my grandson bought a phone from you (not cheap) it was delivered last Thursday and signed by an Amy, Max doesn't look like an Amy.  He went to the Post office Sat. morning and they told him it had been delivered to Amy.

[tobiasd4]

Items don't have to signed for by buyer, posties are signing themselves rather than risk addressee touching pad.

If seller can prove delivery, which they have, then you need to go back to RM sorting office and complain until manager investigates.