If you have the backup on your phone of when your numbers were originally ported in, you can just delete all of your contacts and re-import the original set of numbers.
*I'm not held responsible though if you delete all your contacts and can't get them back*
This is what I did though:
I wasn't happy with my contacts, so I downloaded an app called: ExportContacts. (The phone itself can't handle exporting to gmail format)
I then exported the contacts to the gmail format, logged into my gmail, imported the contacts from that file, the manually deleted/edited the ones I wanted changed.
It will automatically update your contacts as you're working on them IF you have syncing enabled. If you don't have syncing enabled to run in the background, you will have to turn syncing on long enough for your contacts to re-sync.
By exporting the file, you have at the very least another backup of your contacts. The app mentioned above was free when I downloaded, so the only thing this should cost you is a little time.
Good luck
