I don't really get this.

It seems:

1. A lot of secondhand mobile phone sales end in trouble

2. Surely it therefore can't always be the courier as the courier won't always know what's in the package? Especially odd if the phone being stolen is always worth over £200 - courier won't know that detail (no point nicking a £50 phone and risk getting caught, especially in organised crime where the phone may change hands once or twice before resale, each person getting rewarded)

3. But thank you @neovass0 for the tip about oversized boxes! I actually complained to a perfume retailer for using oversized boxes at Xmas but now l know why

4. eBay will push the matter to its limit before refunding the seller, if they do refund the seller. Probably because they want to be sure the seller is being honest.

5. Could it be that the buyer and the courier are the same person or related persons?