I was working in a private firm for a year and...

In case the company terminates work contracts without a legal justification, then the worker can file a complaint at the Ministry of Human Resources and Emiratisation, which in turn will transfer the complaint to the labor court because they do not have the authority to handle that complaint for workers of the free zones.
Also, a worker who is subject to an arbitrary termination of an employment contract can demand compensation for the this terminatio, in addition to end-of-service benefits that the worker did not receive before.
You cannot file a complaint against the employer if you do not have a work visa and work contract.
The UAE Labor Law stipulates:

Article 123
1. Where a worker is arbitrarily dismissed, the competent court may order the employer to pay him a compensation, to be assessed by the court with due regard to the nature of the work, the extent of damage sustained by the worker and his period of service, and after investigating the work circumstances, provided that such compensation shall in no case exceed the worker's wage for three months, calculated on the basis of his last wage.
2. The provisions of the preceding paragraph shall not prejudice the worker's right to the gratuity he is entitled to and the compensation in lieu of notice provided for in this law.