Injustice at Job

Hi , I am working in an IT MNC. Here i had an opportunity to go abroad which was declined by one manager. Then I had resigned from job as I got higher CTC with another firm. Then a manager from current project offered me onsite opportunity and asked me to pull back resignation. The commitment was done that I will travel to onsite from August to November as I have personal commitments after that. The manager has agreed to it.Now, October has started and I do not see any information on my travel. Even after continuously chasing them, I find that I am being ignored. They say now project budget is not allowing this to happen. However , they have made another employee to travel who had joined the project after me. I have asked my manager to revise my compensation if onsite is not possible. They say the company's policies do not allow this to happen. You have to accept the bitter truth. Do I look mad to keep on loosing the opportunities? This is unjustified? Are there any laws protecting employees from this exploitation?