I did the same last week. Had an email off Zebra to say my finance agreement was awaiting activation. I contacted them by phone and they sent me a code via text, which I used to log in and electronically sign my agreement. I received the agreement documents too. For peace of mind I phoned them today, just to make sure it had been activated ok. The girl on the phone took my details and asked me for an agreement number, which I had to look for in the documents email they sent me. The girl confirmed that the agreement was now active and first payment would be taken in April.
My advice would be to give them a call just to be sure, but if you did the electronic sign thingy and received the documents via email, you should be ok.
No harm in checking though for the sake of a phone call, as it is a bit of a weird system.