What can I do if the law firm I hired took more than the agreed fees upon judgment?

I had a civil compensation case (road accident) with a law firm in Abu Dhabi in 2017.

During the initial stage, they had sent an advocate fee agreement mentioning 15% of the collected money from the court by email, I have signed and sent it to them by courier.

But, they failed to provide a signed copy to me and I also forgot to get the same due to my work pressure at that time.

The court judgment and compensation money also came to the lawyer's account, and now my lawyer is asking for 20% advocate fees. I did not agree with the same.

After a few days of this conversation, they verbally agreed to 15% fees and requested to send account details, and I sent my account details.

They transferred money after deducting 20% advocate fees, I have sent many emails to release my remaining amount based on the 15% calculation, but they are not replying or responding to my emails.

Currently, I am in India due to losing my job during the COVID situation.

Please advise how to get my remaining money from them.