Cannot add a second call

[quandan]

current build number: 263
device name: arale
channel: ubuntu-touch/rc-proposed/meizu.en
last update: 2016-03-07 05:48:47
version version: 263
version ubuntu: 20160305
version device: 20160111-51982fc
version custom: 1452441600

Steps:
Set up: you need have at least one contact saved in your device
1.Make the first call
2.When the first call established , tap on the "+" icon to add a second call through contact app

Expectation：
Can add a second call , then the calling page will show two connected calls

Actual result:
After tapping on the second call's number , it goes straightly to the phone call screen ,and the second call cannot be connected , there is still shows the first call

Notes: i made a video about the whole steps