Unreasonable response to complaint involving instant rewards

Problem with instant reward Hi- had an issue with my instant reward today. After arriving at Mugg and Bean Gateway this morning I clicked on the Mugg and Bean option. A barcode appeared for Mugg and Bean -R75 voucher. I did not click on the "done" at bottom. Made my order with waitress. When I looked at my phone again the voucher had gone and the instant reward section had Kauai voucher not Mygg and Bean. I phoned discovery (ref ***9). Waited at least 20 mins to talk to consultanf. Was told to click on cancel on top of voucher. No such option. Was told nothing could be done. Unhappy and confused. I emailed complaints- told ti phone first- crazy as ages to get thru