Is it legal to be fired after being injured on the job?

I was fired after being injured on the job! Told to take time off until doctor apt. they then fired me for the days off when I was told by the person trying to handle my case the days I miss will not count against me since the injury happened at work. After 3 days of calling and leaving messages with no return call I showed up for my next scheduled shift to find out what was going on. When I arrived I was told that I exceeded their points system that I am fired. What can I do I feel I was wrongly terminated? I also told them I would sign off on the injury (which I never did) and seek my own medical attention. They never returned my call to allow that. After being fired I did seek medical attention and it is documented everything that was wrong and the times and days I missed work etc. Is there anything I can do about this?