I am using Firefox on my Galaxy S4 which has a screen size of 1080 x 1920 and Firefox is reporting that it is a Tablet. I am running a custom DPI of 320. The issue is that T-Mobile thinks I am tethering when i am not. Please, I beg you, make an option to select the User Agent that the USER wants. This will allow me once again to use your web browser for Android. Thanks.
The add-ons was my first "go to place" for a solution. Sadly, that Phony add on does not work. I tested this using wifi and went to "Whatismybrowser.com" and it always showed the stock setting irregardless what was selected in Phony. Thanks for your answer though!