My employer is holding my passport and won't let me go on leave. What can I do?

Dear Sir/Madam,

I have been working in Dubai since November 2022, but my employer applied for my visa at the end of December and I received my MOHRE contract and residency in early January. It is a limited contract.

In February, our employer made us sign an offer letter that has different clauses than the MOHRE labor contract. When I asked the employer, they said it was just a formality for our own personal records.

The labor contract and the offer letter both have different clauses (pay, allowance).

The offer letter also states that the company can hold my passport, and even if I complete my probation or work for 23 months and 28 days (before 24 months), I will have to pay them the visa fee if I resign.

I wanted to go on leave due to family matters involving my mother's health, but my employer is not allowing me and is holding my passport. Can they do that?

Secondly, if I resign without a notice period, am I liable to pay for the visa fee (based on the offer letter)? What if I don't pay? Can they ban me on this basis?