I am sorry you're going through this. Let's consult the labor laws in Saudi Arabia to understand your situation better.
Under the Saudi Labour Law - Article 40.1: "The employer may not allow the worker to work for others, and may not hire the worker out to another employer, unless both the employer and worker agree, and provided such agreement is in writing."
As per this law, you can only work for another employer (take kafala) if your current employer gives written consent.
Article 11 of the Saudi Labor Law further states:
"Neither the employer nor the worker may breach the work contract without an acceptable cause."
Based on this law, if your company is not renewing your iqama (which is part of your contract to work in Saudi Arabia), they might be in violation of this law, unless there is an acceptable cause.
However, Regarding the fine they mentioned, there is no specific provision in the Saudi Labour Law that outright states that an employer can fine an employee for taking kafala. They might be referring to a different law or agreement in your contract.
To handle this situation, I would suggest discussing your situation with your employer and reminding them about the Labor Laws in Saudi Arabia. If that does not bring resolution, you can seek assistance from the Ministry of Labor's 'Amarat' service online, which specifically assists expatriate workers in Saudi Arabia. They deal with issues like yours and they might be able to guide you on what steps to take next according to the Kingdom's labor laws.
Please remember that this should not be interpreted as legal advice, but as information to help guide your actions. Do consult a legal expert in labor law for advice tailored to your situation.