Dish TV - Refund not initiated

Regret to inform that even after so many written & verbal complaints,over the past five years I have been trying to get my refund back of DTH set top box. This is because I even paid extra for the replacement of set top box as I had been assured that after finding invoice of year **** company can refund & due to time gap I was not able to provide invoice however once I found & approached your customer care team, who infact get it collect the old set top box,remote with invoice & original SAF/CAF. Now, I recieved email that there is invoice available to deposit the money however a letter from Dish TV stating that refund will be given is not attached,which was never issued or provided to me, hope you will understand that this attitude is not acceptable, as how could I know that why Dish TV did not issued letter/invoice about refund that too in the year ****, moreover invoice is the proof that amount is being credited to the company's account which is proven & still blaming customer is not expected from a company of repute like Dish TV.
Therefore I once again request to please initiate refund at the earliest & oblige.