Yea that link is broke right now, Been reported and being looked into.
Here is another way posted by astrobill;
I found another way for us to view the contract details for each device on our accounts while we wait for them to fix this.
First, click on "See all usage" for one device.
Now, look to the right for a small frame containing the "I want to..." options again...click on "See my contract details" and it now DOES bring up the contract fulfillment date properly.
Check out a fun infographic that teaches you how to increase storage, enhance security, improve battery life and clean your device.