Choose to use the default sim when placing calls from iOS app

Question

We have a dialer app that makes phone calls. Basically, it just sends the dial string to the native dialer and the native dialer makes the call.
When an iPhone has a dual sim, you set which one is used as the default. When you make a call with the native dialer, it uses that default sim. However, when you make calls from our app, it uses the first sim, regardless of which is set as default. The only way to have it call from the second sim, is if you deactivate sim1.

We are not trying to choose the sim from within our app, simply to use the one that is set as primary on the iPhone.

Native Dialer
Primary set as Sim 1 - Calls using Sim 1
Primary set as Sim 2 - Calls using Sim 2

Our app
Primary set as Sim 1 - Calls using Sim 1
Primary set as Sim 2 - Calls using Sim 1
Primary set as Sim 2 (but with Sim 1 deactivated) - Calls using Sim 2

Thanks in advance.

Answer 1

Unfortunately you can't select the sim to call yet.

In the future maybe Apple add that but as you said all calls will directed to the physical sim unless it's deactivated.