If all of your contacts are in groups, follow these instructions to delete them all. 

If your contacts are NOT in groups, please submit a support request asking to remove all of your contacts. Please allow for up to 24 hours for this request to be completed as it requires escalation to our dev team.

Please note, this data is not hard deleted, we will retain sending records to any previous contacts. Alternatively, you can instead opt-out someone you no longer need in your account.