Recovery of money paid for a car without a written agreement

Dear Sir,

I have bought a car recently from one Egyptian through a bank loan from ADCB. The car value to apply for the loan was 24k, whereas we agreed mutually for the final car price as 21k only.

The seller promissed me to return the balance amount (3k) upon receipt of the payment from the bank. Now, the seller has received the money but refused to pay me back.

Hence, I want to take your advice if I can file a case against the seller or not.

Looking forward to receive your reply soon.

Regards,

Najmuddin