Trending @Cognizant; Looking for some advice here.

I am in a project as a non-billable resource but I am assigned work everyday, I do everything a billable resource does including production work.

But I didn't get promoted because I am a non billable resource.

Now my client doesn't want to make me a billable resource as they don't want to have to pay any more. But they are making me do all the work and expecting 'good performance ' from me.

My manager acts like I owe something to my client and keeps asking me to show more visibility, take more responsibility, update about my work everyday etc etc. I work till late nights too because of their expectations.

I actually don't owe them anything because I am not billable. And because of them I lost my promotion.

I know looking for better opportunities is a must but in the meanwhile what should I do? How do I handle this situation? What do I say and who do I say it to?