Non-payment of salary upon termination of employment

I was working as a Civil Engineer in an Abu Dhabi based company since this June 2017. In this August, the company gave me suspension and then termination mentioning that I am not meeting their expectation.

The company called me to the office in this September to sign the cancellation papers. I told them to pay my salary and I shall come after to sign. When I asked my salary, the company sent me one document mentioning that from the work site some materials were missing and their cost is 30000 AED and it should be paid by me.

When I worked there, there were no issues. After 2 months of termination, when I asked my salary they are telling like this:

"The cost of these missing items is 30000 AED. So you have to give 22000 AED to the company net amount deducting your salary. Now, we will give you the offer - no need to give this 22000 AED, instead we will not pay your salary."

I did not sign the cancellation papers. Now the company opened a complaint in MOHRE Abu Dhabi against me.

What should I do?