Hi
I´m an Independant Advisor for Microsoft Community
I will try my best effort to help you.
You need to login your modem, and there change the network name, this name only can be change there. There is no possibility to change that in the computer
Ask your isp how to login the modem to change this.
How to login your modem
Check your ip gateway
Windows + R , ipconfig and see the gateway address in most of the cases this address is 192.168.1.254 or 192.168.0.254
Then put your password of the wireless password.
When you are inside Modem you can change the network name
Let me know if this help you in your issue
Saludos