Pegasus Doesn't Refund Money On Flex Ticket!

I purchased a Pegasus Airlines ticket for the Istanbul–Copenhagen flight on 27 May at 09:40 with the reservation code 1UFCC1. For this ticket I paid 18,000 BolBol points and ₺3,499.8 in total, including the Flex service and baggage. Today, when I wanted to cancel this ticket, Pegasus offered to refund only 18,000 BolBol points and ₺620. When I called customer service, I was first told that, because the flight date is close, a higher deduction is applied. I explained that my friend cancelled a ticket for the same flight on the same day as me and received a full refund, so this justification did not make sense. Then the explanation was changed and I was told that the reason was a 40% off campaign I had used. I responded that I used the same campaign on my return flight, which was on a separate booking, and when I cancelled that ticket today, almost the full amount was refunded and only ₺260 was deducted. After that, I was told that the issue was due to my payment with BolBol points, but I had purchased the Flex service after selecting payment with points and paid for Flex separately. Finally, they stated that it is a “system bug”. Because I specifically paid extra for the Flex service and complied with all the conditions, I do not accept losing a significant part of my payment and being told that the reason is a system error. I find it unfair that I am not receiving a full refund of both my points and cash while other passengers on the same flight are refunded in full under the same conditions. I request that this issue be urgently reviewed and that I am fully refunded 18,000 BolBol points and ₺3,499.8 as I initially paid.