Yes, both Nextiva and Zendesk Talk offer a Free Trial.
Nextiva is designed for Large Enterprises, Medium Business and Small Business.
Zendesk Talk is designed for Individuals, Large Enterprises, Medium Business and Small Business.
Pricing for Nextiva Starts at $18.95/User/Month when Billed Yearly whereas for Zendesk Talk Starts at $9/User/Month.
Some top alternatives to Nextiva includes uContact, Call Center Studio, Grasshopper, Dialpad Contact Center, Vonage Contact Center, RingCentral Contact Center, ipSCAPE and OmniOMS Customer Communication Management Suite.
Some top alternatives to Zendesk Talk includes Nextiva, TalkDesk, uContact, HoduCC, Call Center Studio, TelebuHub, Zendesk Support, VoxDesk, Zendesk Chat and Freshdesk Contact Center (Formerly Freshcaller).