No information about change in Discovery Miles

When Discovery Bank started, I opened an account for the credit card and didn't think much of it. I used to be able to earn +- 3000 Discovery Miles (R300) to 10000 Miles (R1000) a month with the multipliers etc. I didn't notice it until today but I have been earning 1 Discovery Mile (R0.1) fro R100.00 spent which is 0.1%,,, I now earn +-300 Miles a month even my spending pattern has not changed. Called them today and only be told "we have changed the way the discovery miles are accumulated (without informing you)",,,,. This is disgusting,,,