What can you do?
1. Try a factory restore, for some it seems to fix the issue.
2. If the factory restore didn’t work, try this:
– Go into Settings/Mail, Contacts, Calendar, tap on the Exchange account name and turn off the 3 switches.
– Back out of settings, then open Mail, then Contacts, then Calendar to clear the connections.
– Reboot the phone (hold HOME and SLEEP until an Apple logo appears, ignoring “Slide to power off”)
– Go back into settings and turn the 3 switches back on.
You can also do this by deleting the Exchange account, rebooting, and adding it back.
3. If neither the Exchange re-setup nor reboot didn’t help, you can also try to disable the Ping function which runs in the background and drains the battery. Just go into Settings > General > Restrictions and turn off Ping.
Hopefully, one of the solutions will fix the problem.