Misleading salesman in the process of purchasing a property

First of all, I am new to Dubai and I was searching for a villa here. Sometime later I found something I was interested in. I've decided on a villa and many promises were made for it by the seller of the developer.

The seller gave me a good price, a payment plan which suits my needs, included landscaping, 1-year free service charge and other charges regarding the inside of the villa.

I was asking the seller for a confirmation in writing mentioned with all the promises that were made. He told me I will get it only after paying the reservation of 20% from the purchase price. Unfortunately, I believed him and paid the 20% + 4% DLD to the developer.

After asking several times for the confirmation in writing, I still got nothing. We wrote at WhatsApp and I still have the voice memo's and history where we talked about everything.

I have a memo of his voice promising me several times that everything will be realized and that I will get my confirmation in writing very soon like it was promised in the first place.

I had to fly back to my home country due to work-related reasons that's why I wanted to take the reservation form with me to read and sign it at home, but I got interrupted by the seller.

The seller insisted me to sign the form as soon as possible and came to my hotel lobby with the reservation form at 10 pm.

I took an exhausted look at the reservation form and noticed some faults like a wrong payment plan, landscape and 1-year free service charge weren't mentioned either.

He told me that this is just a temporary booking form and it's only about the reservation, just so that I won't lose the villa to someone else who is interested.

He concluded by saying that all the changes that were promised will be written on the purchase contract.

Nevertheless, I've made a copy of the booking form from the printer of the hotel. I've asked the seller several times if there is any hitch in the contract, he made an oath in God's name that my wishes regarding the villa will get done and that every thing has its validity.

The next day when I was in my home country I took a closer look at the booking form. I ascertained that everything was wrong at the form: wrong price, wrong payment plan, and all my wished changes were not mentioned.

In addition, the reservation price wasn't 20% like he told me. It was written at the reservation form that I had to pay 10% of the purchase price. Of course, I complained immediately.

After around 1 week I got a call by the seller. He told me that he couldn't change the price since it was already the best, that he can't include the 1 year free service charge and he could not change the payment plan as arranged before.

He told me he could only realize some few changes regarding the villa but not every thing that was agreed before.

I am really disappointed and I claimed my money back. The only statement I got was that I can't get my money back, because it's not refundable through the booking form.

I feel really messed around and I have never thought that this could happen to me here in a city like Dubai, especially by a big developer with a huge project like this. I feel desperate since it's a huge amount that I've paid.

What can I do? I have as evidence all the WhatsApp memos and the history between me and the seller.

I would appreciate a helpful response or a very good lawyer.