Hi there supergrl9119,
We can provide some guidance.
Pair with an iPhone that uses iOS 10 or later
If you have an iPhone that uses iOS 10 or later, follow these steps:
1. Hold your headphones next to your unlocked iPhone.
2. Press the power button on your headphones for 1 second.
3. After a few seconds, your iPhone asks you to connect. If it doesn't, press the power button on your headphones for 5 seconds.
4. Follow the instructions on your iPhone.
When you set up your headphones in this way, they set up automatically with your other devices that are signed in to iCloud and using iOS 10 or later, macOS Sierra or later, or watchOS 3 or later.
You'll find this information here: Set up and use your Solo3 Wireless headphones
Keeping that in mind, it's normal for the audio to switch to whichever device is playing audio while they're paired.
To prevent this from happening you could tap on the Beats in Settings > Bluetooth while they're connected, then tap Connect to This [device], then tap When Last Connected to This [device].
Take care.