You can use Bitrix24 as call center software. The basic cloud version is free for
up to 12 users and is very popular among small businesses, since it requires no deployment, doesn't cost anything and is ready to use in 3 minutes.
You can also purchase more advanced editions of Bitrix24 that come with open source code and that you can
customize. This is a popular choice when you want to deploy call center software on premise and host it on your own server.
Most importantly, Bitrix24 comes with CRM already included, so you don't have to spend any money on
purchasing additional software and integrating it with your existing call center solution.