Just updated my iphone 4 to ios 7.01 and had to change my password on my exchange account. My exchange account will not verify the new password even though they are the same for both laptop and iphone
It should allow you to change the password in Settings > Mail, Contacts, Calendars > your account > Account > Password > Done
Or you can try to remove your account and add it again in Settings > Mail, Contacts, Calendars > Add Account > Exchange
Hope it helps
Tried that and it did not work
Then try resetting all:
Settings > General > Reset > Reset All Settings
Retrieving data ...