If your Broadband service is not a prepaid account, then you will not be able to add a prepaid service with the broadband. Post pay (contracts) cannot be combined with prepaid accounts.
Has this changed? - when I went to the prepaid link on the Verizon webpage - it says I can add prepaid to My Verizon. I am currently a wireless customer (I have a aircard contract) - Are there more than 1 kind of My Verizon accounts?
Yes, Post pay and pre pay has separate account numbers.
You can use my verizon for both individually, however you can not combine both to have a single view