So it means as long as i do not exceed any of the given limits, i can stick to CC payment? Only when i exceed data/sms/roaming then i need top up via wallet to pay for it, then balance charge to CC?
Eg. overshot by $6, top up $10 in wallet, balance $4 in wallet, once billing comes, CC gets charged $6 after deducting $4 from wallet?
If you don't exceed, CC payment only is fine. If you think there is a chance you might exceed, you need to top-up the wallet. Roaming stops when there is nothing in the wallet - so you will just disconnect.
And the screenshot portion makes charges clear. Assuming your subscription is $10. If there is >$10 in the wallet, then it will deduct from your wallet. If it is less than that, it will take from your CC. They made clear there is no partial deduction so the full subscription is deducted.
This is why I think unifying their wallet in a per-user account makes more sense for users, because if I only used 4 cents of data in two lines, meaning I have $9,96 in two accounts, the next billing cycle means i will be -$20 ($10+$10) from the CC, while the wallet each holds $9.96. This is quite unfair to us customers. When you consider that credits are non-refundable, it's quite a lot of money to throw away - instead of 8 cents, it's $20.