Website to sell Openvpn and Dropbear users.

The client must have a list of their users purchased with an expiration date, who can change their user passwords from the chat or from the web page, once the user has expired, the user will be automatically deleted or the client will be notified to that can update your payment date.
I need to be able to add or remove servers as servers will be added over time. I leave an example image. (Honestly, I don't have much of a budget, but I'm not expecting something unpleasant either, I need a decent job.)
It doesn't have to be a web page and a chatbot, it can only be one.
Time is not an issue as long as they comply and it is well done.
The cost is fixed before starting the work, I don't like that they ask me for more money when the cost of it has already been arranged in advance.

FreeRadius Addon Module y Plus
WHMCS v8.2.1

I also need some way to prevent dropbear users from logging multiple times, limiting to just 1 login per dropbear user..

I also have Mercado Pago de BayresAPP (whmos) If it is possible to add Mercadopago and Paypal to the site.

I leave an example image of what I need.
Serious sale of Dropbear and Openvpn users.

I need the site to be ready in less than 1 week.