Grammar usage

Three of the four can be used.  In is not one of them.  Infosys is a business technology consulting firm.  You can work in the field of business technology consulting.  You can work in Infosys’s accounting department.  But you don’t work in Infosys. 

I work at Infosys.  Infosys is located in a building and that is where I work.

I work for Infosys.  This is close to at, but allows for the possibility that you work outside of the building.  Since they do consulting, many employees likely work for Infosys at the client’s building. 

I work with Infosys.  Infosys is not your employer.  You deal with them on a regular basis or in collaboration with them, but a different company gives you a paycheck.