If you have a cell phone from att and you have the jack black from your sister can you change over to the black jack for free?

If you have a cell phone from AT&T and want to switch to a different device, such as a BlackJack from your sister, it typically depends on AT&T's policies regarding device compatibility and activation. You may be able to use the BlackJack for free if it's compatible with your current plan and is not locked to another carrier. However, you may need to complete the activation process, which could involve some fees depending on the circumstances. It's best to contact AT&T customer service for specific guidance on your situation.