how do i deactivate my account
If you want to delete your Todoist account, please click on the gear icon in the top-right corner, go to Settings -> Account and use the link at the bottom of this window to permanently delete your account and all data associated with it.
Note - if you've set up your Todoist account with your Google Account, you will need a Todoist password to confirm the deletion. It can also be set in the Account settings using the "Edit" link in the "Password" section.
How can I reactivate my account after accidently deactivating it?
Do you mean activate your Premium status? If so, please send us the order number of your payment, so that we can add the remaining time of Premium to your account