Hello moms, has anyone encountered the situation that we live in Moscow…

Hello moms, has anyone encountered the situation that we live in Moscow and are attached to clinics but there are no pediatricians' vouchers available at the nearest time? We registered through the Government Services app for another clinic and there the doctor said that they wouldn't be accepting us because we are from another clinic. Does she have the right to refuse? And if so, why can we register with her then and she refuses to accept us? Where should we turn to after being refused an appointment?