The best Free Call center Application

Hello Guys,

Please I need a recommendation on the best call center application I can use for my business (On Premise Call Center)

Have you checked out the Unified Service Desk that comes with D365? https://docs.microsoft.com/en-us/dynamics365/unified-service-desk/admin/call-center-challenges-how-unified-service-desk-can-help?view=dynamics-usd-4.2

There are a lot of add-ons you can use - but I’m not aware of any that are free. What phone system are you using today?