Plans before March 2016 do not come with shock free data, so you won't see it. If you want the feature you will have to switch to a plan that included it. If you have a good grandfathered plan better than what's currently available, I'd instead use the data limiting features built into the phone.
Thanks for reply - I am on the new $60 for 2 gb + bonus 2 gb plan which I signed up for yesterday. My previous plan also was a SFD plan (it said so in several places), but also only showed a place to select SFD at 50% and 90%. So I assume by your response there is suppose to be a box to tick 100%?