1. A system for managing multi-tenant callback services for call centers comprising: a plurality of tenants, wherein each tenant provides one or more sets of configuration data; a plurality of call center applications from one or more vendors for assisting a plurality of call center agents; and a queue callback application among the plurality of call center applications for managing callbacks to connect callers to call center agents over a public switched telephone network, wherein each set of configuration data is customized for a tenant and associated with one or more of the plurality of call center applications, wherein the plurality of call center applications can support multiple tenants, utilizing one shared installation of the one or more of the plurality of call center applications, and wherein each tenant has a virtual partition on which instances of the shared installation of the one or more applications is run.