HappyEasyGo — Fare difference charges

My flight had cancelled because of covid, and im trying to reschedule my flight for december. The HEG staff is giving me a fare difference which is high as compared to the actual difference. When i raised the complaint for same they have been dodging it since 6-7calls saying they will get back in an hour. They also added that the fare chnges dynamically which does but my sector tickets have been on the same price for one week. They are looting the customers and the customer service is not even clear on the fare calculation. Worst grievance resolution customer care ever