I believe is Grab system got issue. I have in app chat them but no replies for days. I ended up Facebook chat and did gotten reply saying they will check with the relevant department. But still no hear back from them. I have check with my bank which tell me no issue with my card. I can spend on other stuffs just that cannot use at Grab.
Grab ever have similar encounter in the past but is on credit cards. I believe their system has issue. It needs more people to feedback to them to get them start taking it seriously it seems.