You can only claim promotional items if they are available to do so linked to your purchase.
Can you link to the offer please ?
Have you seen promotional information saying you can claim free earbuds either from the business you purchased the phone from.
If so there should be a claim form in the promotional information.
There will be Terms and Conditions and claim criteria with start and end dates @izzy_B
i.e I can see >
https://2021.samsungpromotions.claims/galaxy-a-buds/en-GB and https://2021.samsungpromotions.claims/galaxy-a-buds/en-GB/qualifying
I wish you all the best. 
