PPI claims: linked cards

With the help of Resolver, last year I successfully reclaimed some money for PPI from Egg and Mint Cards. In the new tax year I am claiming for PPi from my longest standing credit card, Barclaycard [ at least 20 years ]
I have just received a letter which states: "Our records show that you have had other cards linked to this card. These linked cards are shown above and have been included in our investigation. Our records show that this complaint has already been resolved. A letter was sent on the 20 June 2017 confirming the outcome of our investigation. "
I only claimed for the discontinued Egg card but it seems that they have included a Barclaycard in the in repayment as well. Given the card number changes at each renewal would I be correct in thinking that Barclays are only including one card for the 3 years that it is operational in their calculations.
I hope this makes sense and someone may have some suggestions as to whether Barclays are trying it on.