Bitrix24 is #1 free account management software for small business. Unlike most account management solutions that limit themselves to CRM, Bitrix24 gives you a number of additional features. For instance, Bitrix24 comes with free full featured contact center. This means your clients can contact you via email, phone, social networks, website live chat and you'll be able to provide support via any of these channels, storing the entire history of all communications in one place.
Second, Bitrix24 comes with a full featured quote and invoice system that supports retainers and recurring invoicing. Third, there are a number of workflow automation features that help your account managers with routine tasks and alert supervisors if clients aren't satisfied. Email marketing and client reactivation tools are available as well, making Bitrix24 #1 free SMB account management software.
Bitrix24 is available in cloud, on premise with open source PHP code assess, and as Android and iOS apps.
Bitrix24 CRM manual is available here.
If you are interested in buying self-hosted editions of Bitrix24, which come with API, CMS and source code, can be easily customized and integrated with other tools, please download a trial version here.