Credit Card fees - am I being unreasonable?

I'm having an issue with my Standard Chartered AsiaMiles CC at the moment, and I'm wondering if I'm being unreasonable?

I've had a few HKD-denominated transactions recently which were from AirBnB, who apparently are considered an international vendor and therefore subject to a 1% service fee (even though they charge in HKD so there's no fx). OK, fine, that's probably in the T&Cs somewhere..

I've had those transactions refunded recently, and SC have charged ANOTHER 1% on the refund.

- I'm charged $1,000HKD, SC charge me $1,010
- The merchant refunds my $1,000HKD, but SC only give me back $990.
- Effectively they take $20 for nothing ("Mastercard fees").

I'm sure this is their policy and in the T&Cs...but does that sound right? In my view, fine, charge the 1% on the original tx, but when that tx is refunded (effectively reversed), then refund the full amount. You can't charge 2% for doing nothing.

(FX transactions I can understand, but these are HKD transactions)

I don't think I've ever had this in 6 years of using AMEX or Citibank cards in HK, but am I being unreasonable?

Thanks in advance.