The Flex package you describe does exist, I have it, but it is a classic example of left hand not communicating with right hand. It took a whole day on the telephone to get it ordered. However if you don't have your telephone service tied to it, you are in for a world of grief. Just about every interaction you have with the billing or support folks is tied to your telephone number. For reasons I don't understand, my telephone service (Verizon), is still on the copper pair, even though the TV and Internet are FIOS, and the wiring is in to make the telephone FIOS (just need to connect the two wires), but Verizon for some reason doesn't want to do it.
It takes an act of G-D to get a copper pair telephone 'connected' to your FIOS accout. Without the connection, your interactions with Verizon on billing and/or support issues are an exercise in futility. Your calls to Verizon will ALWAYS end up with people who know nothing, and can do nothing. While my Verizon bills for the Flex package has a phone number on it, it isn't a real number, and it is worthless for reference.
Somewhere at Verizon, left hand needs to communicate with right hand.
I upgraded to the $79.99 "double flex" bundle in less than 5 minutes.
I logged on to my account at Verizon.com and selected My TV -> Add/Change Channels & Plan. There was a link for "ExtremeHD + 20/5 for $79.99" -- I clicked that and got the option to order online via representative chat. It took about two minutes for me to get a representative and another three minutes for them to upgrade me to the "double flex" plan.
I just ordered the flex plan today. I called 888-591-6076 and was in contact with a FiOS-knowledgable rep in 30 seconds -- no hold time. This was a "Call us about bundling" phone number I found on the FiOS TV verizon web site.
I have to say that this is the best customer service line that I have ever called at Verizon. It took the lady here less than 20 minutes to not only "upgrade" me to the Flex bundle (I dropped my phone from the Triple Play Bundle - something the normal customer service line wasn't able to do) and get rid of the ghost DVR that has been on my account for the last two months that I returned back in October. How come VZ can't get these people to work at the normal billing/account changes on the 888 553 1555 number?