Yes, you can change the character limit! Well, not everyone can, but it is a setting that admins and orgs admin can easily modify. For more information on how to do so, please see Adjust message character limits.
Note: Messages sent through our Campaigns feature have a different character limit, which can be found under Settings > Campaign Settings > Character Limit. Like its counterpart for one-to-one messaging, this setting is only accessible by admins and org admins. More information can be found here.