Chat Function in the Premium Planner Card

If you mean the Comments/conversation section inside a task, Premium plans don’t necessarily have the same experience as Basic plans. Upgrading isn’t simply adding features to the existing task cards, so this may be a feature difference rather than a setting you’ve missed.

Try opening the Premium plan inside Teams, then open a task and look for Conversation or Chat. Where available, this uses a Teams conversation rather than the Basic plan’s comments.

If that option isn’t there, there isn’t a general switch in plan settings that restores Basic-style comments. A Teams channel thread with a link to the task is a workaround, but it won’t put the discussion back inside the card.

Don’t assume your old comments were carried over either—check the original Basic plan if it’s still available before deleting anything.