Who Designs Glo,mtn,nokia,samsung Billboards?i Need A Designer

Hello there, I am coming up with a project that pushes towards the media side. I need to know those companies that does the designs for Glo, MTN and all those multinational companies' billboards. You know the glo advert with some guy carrying a guitar, something like that. Please does anyone know any of these agencies as I need some info really urgently

Please check out The company ICStudios on the website www.icstudiosng.com. i'm sure we can handle all you need. thanks