Once a campaign is sent, changing the content is not possible. Moreover, it's not possible to unsend a sent campaign.
If you'd like to rename a sent campaign, you can do so by:
Clicking the More button on the right-hand side of the sent campaign
Selecting Rename from the dropdown
An alternative to making changes in a sent campaign is sending a follow-up email to your subscribers. It can simply be a heads-up correcting the mistake on the first campaign. Trust us; your subscribers might even appreciate you for making a follow-up!
🔗 Changing (wrong) links is an exception, as you can edit URLs on sent campaigns. Note that links can only be updated within 12 hours of sending and only if you are on the Free trial or on a paid plan.