Are you referring to the circle with the diagonal slash as the the 'no' icon. If so that means you have no cellular signal. Since I don't know which device you have, if it is a Verizon device, I do recall at one time they had a phone(s) that when you turned on Wi-Fi (as you do in the picture) it disabled the cellular connection so you weren't using your data plan.
So try turning off WiFi and go outside for a clearer signal and see if it goes way.