The amount for my monthly icloud bill is not the same as the amount took out from my bank.

Vichvanich Said:

"The amount for my monthly icloud bill is not the same as the amount took out from my bank."

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For Financial Assistance, Contact Apple Store Support:

You need to contact Apple Support Directly. This is a User-to-User forum. We are all volunteers. So, as you may suspect, no one here has access to that information — and that is a good thing, BTW. That’s why for Financial Assistance, you need to contact Apple Support. They’ll see what’s going on and will run you through the fix.

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I’d start with your card issuer, it’s not from Apple

That's likely tax or something else

I just found that there is a card fee for overseas transactions in Singapore Dollar. It seems to satisfy this situation.

You can refer to this page: https://www.dbs.com.sg/personal/cards/cards-rates-fees.page

According to the document provided by DBS, it seems that the iCloud fee transaction is handled overseas with Apple Inc. despite in Singapore Dollar. Calculated based on the 2.8% card rate, the final cost for iCloud is exactly

(1 + 0.028) * S$3.98 = S$4.09144 = S$4.09.

Perhaps this is the reason for the final SGD4.09 fee.