We do have an extra coverage on our daughter's IPhone 5 through ATT. She is almost 19 and she has had an IPhone since they came out. We have used the warranty in the past and she has ended up with a brand new phone more than once, once dropped in toilet at school, once it just stopped working, once it was stolen at school, BUT, we were able to get a new one at the discounted price via the warranty.
Hubby and I also carry IPhone 5 through ATT and we do not have the extra coverage on ours.
FWIW... A cracked screen can be replaced for less than $100, although in some circumstances, it will void part or all of the original warranty. There is a small shop here and my hubby has had his screen replaced twice as well as the battery. He refuses to use a case, therefore, his is the one that gets cracked.
The ATT store is located in the same shopping center and the associates at ATT will tell you to go to the Cell guy for repairs.
Check around and I bet you can get a screen repair for less than $100 and your phone will be perfect again.