Hi @Mingin, thanks for your post and sorry that you're having issues with your volume.
As @Ernie_C and jb66 have mentioned, the TV360 doesn't have the functionality to control the volume on your TV separately, it simply just mirrors the TV's functions of doing so when you use the remote to do this.
If your TV remote isn't changing the volume, then it does appear the fault is with your TV I'm afraid!
I'm sorry I can't help further but if you've got any other queries on TV360, please don't hesitate to let me know and also you can check here too.
Regards
Tom_W