The American University of Science

I am an expat teacher here. They work with the Agency to introduce me a rental apartment. I had to pay a deposit and sign a one-year contract. After probation, I didnt sign the labor contract so I didnt stay in the apartment anymore. The point is, the immediately replaced me with another teacher and countinued the rental contract, also received her deposit. Meanwhile, the Agent confirm that they didnt collect the deposit from the one who replaced me. However, they didnt refund me the deposit. How can an educational institution behave like that and withhold money from staff?