Reliance Communications — postpaid final negative bill amount to be refunded

Dear sir,
I had migrated from reliance gsm postpaid to jio in september 2017. My final bill value is -1312. One of their customer care operator said that the excess amount which i have paid will be refunded through check within 60 working days., but it's already been more than that and iam trying all possible ways to reach them and sent a mail to appeliate authority last month. Even then i received no responce from their side. So, i request to solve the issue as early as possible.