Paid Direct Messages Plugin for Wordpress

We need to have a Plugin which will charge for each Direct Message. The User wanting to pay for each DM from a Vendor / Seller would pay for Credits. Each Credit value would be set by the Vendor / Seller. Upon each DM sent from a submitting User, his/her account would be deducted 1 credit. We would also like a Notification once the Account $ Value or Credits reach a certain level as defined but the submitting User. This Plugin would be a Stand-Alone plugin and be used on any of our sites. And ideally integrate (but not necessary) with Woo Commerce / payment systems. Please message if you have any questions.