known issue,there have been many phones cracking right there,.
go to my.memova.com and sign up, this is link you to the app store for the iphone app as well, this is a GREAT lil app that will take all your contacts and sync them to your free online account.
upload your contacts with the app, backup the rest of your files,....
Do a full restore to default to wipe the phone.
Go online, to apple support, make an appointment at the genius bar, DONT BE LATE! they cancel after 5 minutes..
show them the cracks that is a known issue, wait 10 minutes with the pimplefaced wannabee hipster brat to hand you your new phone.
then, with the new phone in hand, re-download the my.memova app, hit sync and all your contacts are back like they were before..
now your all set.