The text messages on my Nokia C1 get scrambled. The messages get out of date and time order, both received and sent. It also mixes up senders. Messages that I know came from one person are showing up under another person's incoming message. It does not seem to matter if I an in conversation view or inbox view.
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My first suggestion would be a factory reset of the phone. This sounds like a software issue.
To restore the phone back to factory conditions, select Menu > Settings > Restore factory sett. and try Restore sett. only first. This will not erase any of your personal data on the phone. If this does not fix the issue, I would then suggest the Restore all option. This resets all preference settings and deletes all personal data, such as contacts, messages, media files, and activation keys.
Let us know how it goes!