Air India Express — Flight refund 16th April

IX840 DXB -GOI departing 26-Apr-2023
The above flight was cancelled as it was rescheduled by the airlines and i received a notification stating that i can cancel or reschedule without any additional charges as i was not comfortable with the time i canceled the flight by calling the airlines hence no response from airlines i contacted my agent through which i booked that is make my trip and they helped me connect to air india express after 4 hours of struggle the lady agreed over refunding 1500 AED within 15 days after that I'm following up with make my trip and no response as they say air india express isnt responding to their calls nor emails. How can any airlines act so irresponsible. Please help me get money back