That's your Advanced Calling. Go into your settings, Advanced Calling and see if it's activated. I do believe you can activate it from your phone. Also, you must have Data on to use it and the other person (your cousin) also has to have it activated.
Nice... I just looked into this on their website and found the following:
Advanced Calling 1.0 is available at no additional charge, and HD Voice is included in existing plans.
HD Voice calls are billed as standard voice calls according to your plan. No data charges apply.
Mobile-to-Mobile calls that happen to be HD Voice calls are charged just like traditional Mobile-to-Mobile calls and are billed against your monthly minute allowance according to your plan.
A video call is an HD Voice call combined with real-time video. The voice portion is billed as a standard voice call, according to your plan. The video portion is billed as data, according to your data plan. No data charges apply to video calls transmitted over Wi-Fi.
Note: An average 1-minute video call uses about 6 - 8 MB of data. The actual data consumption of your video call may vary. You can estimate your data usage using our online Data Usage Calculator.