Some gyms want to create a round robin type phone call system. This scenario means that when an incoming phone call comes to your Grow number, it will forward to all the phones you want. Then, the first person to answer the call is connected to the caller.
All you need to do, is set up a FREE Google Voice number.
Here's how to accomplish this.
Go to voice.google.com
1. Click on "For personal use"
2. Click on Web
3. After you create your new Google Voice number, Click the Gear "Settings"
4. Scroll down to the setting section to "Link Numbers" and add all the phone numbers you want to be connected to this account
All the numbers added here, will ring at the same time when an incoming call comes in
5. Enter the phone number you want to link to this account
Google will then send a verification code to the new line