In fact, 3.3GB is also enough to store about 4 hours worth of speech recordings per day for a year for every single person using the best available compression. Double that since you don't need both sides of the call, and consider that the average amount of time spent on the phone is substantially less than 8h, and they can already store full voice for all US calls for many years in an exabyte.

Given that the 1 exabyte is a low order estimate given the size of the Utah data centre, you have to wonder just exactly what they are actually storing or planning to store there. If someone had access to it (and I'm not saying I think the NSA do), the site is physically big enough that you could fit sufficient storage to keep years worth of voice recordings of the total global phone call volume.