booked flight to find out later this is only for umrah passengers and amendment costs 150/Person

I recently booked a ticket online for my sister and her son to travel via flyDubai from Dubai to Jeddah. After making the booking and payment online i received an email that this flight is dedicated to passengers traveling for Umrah only. When i called to make the amendment and book a different flight i was informed that there will be a penalty of 150SAR per person. I informed that team that i was not aware that this flight is only for Umrah passengers there was no warning or alert when i was making the booking but i was told by the agent this is published on the website that all flights numbers 7000-7999 are for umrah passengers only. I was told to write to the email address to make a complaint but to no avail. I am sure i am not the only one out there who booked one of the umrah flights to later on find out that regular passengers cannot travel on this flight and have to pay added penalties to change this.
I recommend dont book flights with flydubai online you will never know what exactly you are buying. be prepared for a surprise.