In order to earn a call-up you have to get 5 wins in 10 games to move out of the Freshman tier. You can get bonus wins if you use an inferior team against your opponent. For example, if you beat a Tier 1 team with a Tier 2 team, you get 1 bonus win so that equals 2 wins if you beat them. If you beat a Tier 2 team with a Tier 3 team, the same bonus applies. And if you can manage to beat a Tier 1 team with a Tier 3 team, you get 2 bonus wins for a total of 3.
Be careful though because this achievement can glitch out on you. After you get enough wins to earn your call-up, it will ask you if you want to immediately move up or if you want to stay in the Freshman tier to try to earn the trophy. If you stay in the Freshman league and then anything at all happens like you get disconnected or your Xbox freezes, when you reload the game you will be in the next tier but you will not get the achievement. Which then means you have to either earn another promotion, or lose 3 games and get demoted and start over from scratch. So beware of this if you choose to stay and go for the Freshman trophy.
Edit - Apparently this glitch can be permanent because I got demoted back to Freshman and earned the call-up to JV again and the achievement still didn't pop. Thanks a lot 2K. Only other thing I can think of is that I got my last 2 wins for the call-up by my opponent disconnecting so maybe it only counts if you finish the game? That's horrible if that's the case because people quit or lose connection all the time. Maybe this is why so few people have the achievement.
Edit #2 - Judging from some comments here and from my own personal experience of trying again and getting 5 more call-ups and still not getting the achievement and then finally winning a trophy and the achievement popping right away, I think that the achievement is actually for winning the trophy and not just getting called up. So if the achievement is not unlocking for you, make sure you win the trophy and you should get the achievement.