Reloaded BP 8 times with tac received,  only 4 successful ones, prolly need to call CS to check whether 8 or 4 transactions went through

it is sharing limit. Seems something weird. Only the limit is different happen if u have supplementary CC

It's combined limit. And yes, just call CS to request for the flexipay.

Looks like 8000 to me. The available balance is per-card but ultimately tied to your credit limit which should be 8000

Someone said before s/he get to spend a bit above the credit limit. I don't remember which bank though. Unless you're saying that you've spent like 2k-3k above 8k, then I don't know la.