How can I Disable one sim card on iPhone XS Max

How can I Disable one sim card on iPhone XS Max.

I have two sim card (physical) one for my Hong Kong number and one for my Australian number.

When in Hong Kong, I was charged (by Telstra) for receiving phone calls and SMS messages to my Australian number. (data roaming already turned off)

I want to be able to fully disable either the Hong Kong Sim card or the Australian Sim card when in either country.

All I can find on the web is to Remove the sim card i do not want to use.

This defeats the purpose of having two sim cards. i got this phone so I didn't have to keep physically changing sim cards every time I travel, which is very often.

i spoke to Apple this morning and they inform me that there is no option to disable one sim card but is something they may add later.

Just wondering if anyone has found a workaround to this IOS omission which has turned out to be very costly for thousands of users caught with the same issue