Maybank do have buffer limit, especially AMEX, personally have tried it allows more than 30% of current limit, only for certain retail purchase. Online transactions usually will not go thru.
Not really identical but similar issue.
My supp card swipe for 50k (CL) last month (slightly over actually), but I had top up into my CC account before next billing cycle.
So when she tried to swipe for another 5k, it was unable to get through (even the leftover CL shown in M2U is more than 5k).
Called CS and were told that for supp card, the limit for each month is equivalent to CL, even you have top up the amount.
For principal, there is no issue, you can spend any amount and top up, as long as the actual amount owe bank < CL.
As I was away and unable to swipe for it personally, I tried to ask for temporary CL increase.
Finally the transaction went through.
Upon checking M2U, I saw that CL only increase for 1k.
I am not sure how they actually calculated the amount.
I believe we can go beyond CL for about 10%.
Note: I am not sure if direct cash deposit into supp card acc number will increase back the CL
My CL negative since 11.11 and no issue using both AMEX and FCB for online and other transactions. Maybe not yet reached the buffer