Incoming calls during active calls cause multiple issues

[xxxserxxx]

If a call is in progress when another call comes in, the screen shows the incoming call, but:

1. A ring tone sounds, and continues to sound while the call is incoming, playing over the current call. The person on the other end can't hear it, but it makes hearing the other person difficult.
2. The incoming call can't be rejected; trying to do so terminates both the incoming and the ongoing call.

While this could be considered a feature, most mobile OSes allow joining an existing call with an incoming call. This is not possible with the current Phone app.

This is:

• Linux FuriPhoneFLX1s 4.19.325-furiphone-radon Camera app "Press and hold to use the timer" info message pops up every time i want to get to menu #1 SMP PREEMPT FuriOS 14.0 Tue Jan 27 18:58:58 UTC 2026 aarch64 GNU/Linux
• Phone from debian-forky-main 49.1.1 (which came with the phone or was updated through a system update)
• US Mint (MNVE), perpetually VOLTE