Call duration label

![call3](https://cloud.githubusercontent.com/assets/2544251/4877951/57bf0396-62fc-11e4-9c03-1a9cab01bac1.png)
![call4](https://cloud.githubusercontent.com/assets/2544251/4877954/6aa424e6-62fc-11e4-896c-d2facc67d091.png)