Which CRM fits the business model: subscription?

Question

CRM

The bottom line: there is a project in which there are several tariffs and hundreds of clients, each client renews or does not renew the N tariff every month, at first he led everything in Excel, but now it has become almost impossible.
I tried different CRM systems, incl. and paid, I did not find one that was created specifically for the business model: a subscription.
Please do not offer any amocrm and bitrix24, this is not at all.
Ideally, there should be an API so that I can set up billing and my service so that the subscription is automatically disabled if it is not renewed.
In fact, BILLmanager is suitable, but it was created for hosting, but I'm not a hoster, I would like a specialized solution. You don’t really want to write for yourself, it’s easier to buy a ready-made solution.

Answer 1

CMS Joomla! 3.6 + improvements (not much if you know the API).
I can create if the BP is known in more detail.
Those. as I understand it: each tariff has a different cost and turns on automatically every month (extends), removing from the user's balance immediately for the next month. Right?
If 2-3 tariffs are connected at the same time or tariff options / discounts - then how is the calculation carried out?