Create a API to capture phone calls VBA/COM and .NET API

I have some software called remote phone call (justremotephone), I would like to use this software to capture the incoming calls numbers, messages and want to make outgoing calls, sent messages,
I understand it has an API that allows programmers to access its features, please refer the below link https://www.justremotephone.com/sdk/Help/?topic=html/N_JustRemotePhone_RemotePhoneService.htm

Let me know the timelines and cost.