Double data is a promotion right now.
Normally it's $30 for 2GB of data, but now with that promotion you'll get 4GB for the same cost.
Same for their higher plans as well, the data get's doubled for the same amount.
Do I register for data on receipt of the phone?
Sorry for the dumb questions but I haven't dealt with Verizon before and it seems odd that I can't select data along with the voice plan from this offer page.