Account cancelled without any notice

I have recently received a Medi Wallet card from Specsavers to spend at Clicks. I used it and earned R 250 rewards which I did not use. I then app**** for a credit increase and based on this Specsavers/Mediwallet cancelled the card. This was done without communicating it to me and now I lost the rewards that is rightfully mine. It feels a bit like false advertising or even ***** if they can just take back the rewards that was rightfully earned. This is ridiculous for them to just cancel everything even when I was paying my account diligently.