Need marketing advice – how to market this app with no money

We have an app-based platform called Simply C2 which is meant for our CRM clients' customers to directly log complaints in the connected CRM account of our clients.

It is free for the end customers.

Our experience has been that our CRM clients see this platform and want it customised and rebranded for their own use.

This gets us additional business but something we are not happy about. We would rather everyone simply used the platform. Why? Because, that ramps up platform usage rather than us having to maintain multiple code forks.

We do not have money to market b2c. Our idea was to market the CRM + Simply C2 together to clients where Simply C2 is a compelling value add (replace your call centre) and get our customers to spread the usage of Simply C2 among their customers.

Any ideas? What should we do?