Dual SIM -Setting for Only Using One Line/SIM for All Outgoing Phone Calls?

Hello

I often travel internationally with my iPhone XS. It has a two phone numbers via the dual SIM feature (one via eSIM and one via physical SIM). I'd like to be able to "force" the phone to always use one SIM/phone number for ALL outgoing calls.

Unless I'm missing something, there's no easy way to achieve this. For data, it's simple to make sure the phone only uses one SIM. That's not the case with phone calls. It's quite often that I'm hit with roaming charges due to calling something from Contacts or Favorites using the "wrong" SIM/phone number. When dialing a phone number manually (inputting the number), it's easier but it's still an extra step that shouldn't be needed.

It's a huge pain to go into each individual contacts and change the default settings for calls (which SIM/phone number to use for calls to each contact) and then have switch it back again when I return home.

I need to keep both SIMs/numbers active so I can receive incoming calls to both (and so iMessage/FaceTime keeps working with both SIMs/phone numbers).

Can someone help with this?

Thank you.