Discovery credit card ********** activities

I had a discovery credit card for about 5 months and used it quite a lot in that time and was very deligent in paying my account however I no longer needed the credit card so I paid off the balance I owed , the final figure was provided by discovery credit card department. I received confirmation of the closure. A week later I received a message that I had been credited with discovery Miles but when I tried to use it I could not. I contacted the credit card call center who told me that my account was closed and I had no balance owing to them however they have forefeited the discovery Miles I accumulated while I had the card. This is certainly ******* because if had been owing them an amount they would not have closed my account until I paid what was due and that is what they did, yet when they owe clients money and the account is closed they forfeit what is owed to the client. This is so like the SA government system because we have no recourse. This is just another way of how big institutes are given license to rob clients. Please note that I accumulated the Miles while I was a ligitimate client.