Can you be a little more specific here? Have you backed up your contacts to your computer? Cloud, anything? Most likely an easy fix if you can give us a little bit more information.
OK. Were the contacts that you lost synced with the Exchange account? With a deactivated account they would stay on your iOS device until you delete the contacts portion of the account or the entire account. Did you get a dialog box like below (except with contacts "on") when you deleted it?
it might be possible i dont remember, however i thought all the backup goes to my icloud anyway.
the exchange was my universities email but ive graduated and they deactivated the email. ive contacted them now but i dont think they will help me anyway
This used to happen to me a lot after a game that took a lot of memory would crash on my 4S. I would have to go into Settings, turn contacts off, reset phone, turn them back on, solved. Weird though because it happened again today and I have long since deleted that app. Definitely ready for a new phone