1] Using no-code iPaaS tools like Integromat(Make.com), Zapier etc. - These tools have modules of CallRail as well as HubSpot. You can connect them to your account and use the available functionalities to complete the integration.
2] Using APIs of the apps to integrate. - For this option you need some coding knowledge or a developer who already knows how to work with APIs. - You can either create a scheduled script that runs periodically to sync the data or host the solution on cloud platforms for real time integration.
Do connect if you need help. I have 7+ years of integration experience of various tools out there in the market.