Actually, I tried to dequeue the theme’s custom fontawesome css stylesheet but it didn’t work. However, I used Chrome Inspect tool and found out that the font of these icons changes to “Segoe UI” even though I have set the font-family etc so what I did was change the css font-family to the ones used by Font Awesome for the class of all of these icons and it worked fine. 😀
Thank you so much for your help.