Hello there, JJHS Cheer.

You can follow Rustler's suggestion. You can create a dummy customer with the group name and make the members a sub-customer. This way, you won't lose their historical data. 

First, let's create a dummy customer. Here's how:

1. Click Sales, then go to the Customers tab.
2. Click New customer, then enter a desired group name.
3. Click Save. 

Then, make the member a sub-customer. Here's how:

1. Choose a customer, then click to open the profile.
2. Click Edit.
3. Put a check mark in the Is sub-customer box.
4. Click the Enter parent customer drop-down arrow, then choose the group name. 
5. Click the Bill this parent drop-down arrow, then choose Bill this customer.
6. Click Save.

I've got screenshots to guide you.

You can leave a comment below if you have more questions. We'd be happy to answer them.