SunExpress Issue: Family Separated Despite Empty Seats In Same Row

I have a reservation with SunExpress on flight XQ869 from Rome to Izmir on May 5, 2026, under the booking code SG6Y39 for three family members. While checking in, we saw that three seats were free in the 8th row and much more rows, but the system assigned us to different seats, and now one of our family members is seated separately from the rest of us. As we are travelling as a family, we would like to sit together, especially since there were free seats in the same row at the time of check-in. We have not yet contacted customer service, because the flight is still two days away, but we would like this issue to be resolved in advance so that we do not experience stress and confusion at the airport. I kindly request that SunExpress arrange our seats so that all three of us can sit together on this flight without any extra charge and confirm this change in writing.