Chat is not set for communication, but for commands instead.

I found out that my chat doesn't reach to anyone unless I'm using the /say command. it seems that the chat is not set for communication but commands. I'm an OP, so i can use the /say command, however member-level can't use /say but only /msg or /w instead. also using /say makes it [Username] but without it its <Username> which is definitely doesn't look like a chat function. is there any way to make the chat automatically function as communications?