Hi @Samsung_45BpUzA, I hope you are doing well.
Can you please provide me with the following information:
• Mobile carrier
• Current baseband version (found in Settings>About phone>Software information)
Some carriers such as AT&T require WiFi in order to download the system update. If AT&T is your carrier, this is the cause and there is no way around this as this is a carrier restriction.
I hope this helps!