NextCall is described as 'Nextcall is the best way of tracking how often you're calling your clients, or perhaps, even your mother'. There are five alternatives to NextCall for a variety of platforms, including Online / Web-based, Self-Hosted solutions, SaaS, Cloudron and Etebase. The best alternative is EteSync, which is both free and Open Source. Other great apps like NextCall are Monica (Freemium, Open Source), Dex (Freemium), tinyblu (Free) and Keep My Friends (Paid).
Dex is a personal CRM designed to be much easier than a sales CRM. Dex reminds you to keep in touch with the people you care about. Easily visualize, understand, and manage all your relationships for free.