Once you have created a series of services in WP, you can easily change the title of the series with just a few clicks. Here's how:

1. Hover on the Account link under your profile name
2. Click on Manage Services
3. In the list of services, find one of the services of the series you'd like to change the title to
4. Click the title of the series to be changed
5. You should see a list of all the services in the series. If this is the series you'd like to change the title to, click the Modify Series Title link below the Service tab.
6. Enter the new series title and click Save