4. To claim your Headphones, you need to go to
https://sonyheadphoneoffer.co.uk and complete the online claim form between 18/06/20 and 31/07/20 ("Redemption Period").
Claims website on 18/06/20: 'Please do not claim until 14 days after you have received your handset.'. Meaning you are not allowed to claim until 02/07/20 which is NOT what the T&Cs say.
Again, a regular customer who only shops for phones every other year or so cannot be expected to be up to date with common practices of how&when to claim promotional devices. T&Cs is all I have to go on...
6. If you return your Qualifying Device your Claim will be invalidated, and you will not be entitled to claim or receive the Headphones under this Offer.
This condition cannot be, by a reasonable customer, to mean they are not allowed to claim. It simply says the claim will be invalidated. The action of making a claim and that of a claim being invalidated are not equal. In order for a claim to become invalidated, it must first be applied for.