Citroen Vehicle First Maintenance Appointment Scheduling Challenge

I have been trying to schedule the first periodic maintenance for my Citroen vehicle with license plate ****D996 for almost a week, calling authorized service centers in different cities, but they can only offer appointments 15-20 days later. When I used to call service centers for another brand (also French), I could easily get an appointment within 2-3 days. If you can't manage this, why have you grouped three brands together?
Additionally, I traveled abroad with my vehicle and started calling service centers before leaving the country, hoping to get the maintenance done upon my return. However, I was informed that if I had the service done abroad, it would not be covered under warranty. Now, if I exceed the mileage limit, I am concerned that if any issues arise, I will not receive support and will be left at a disadvantage.
I request immediate assistance in scheduling my vehicle's maintenance. Thank you.