DENVER (KDVR/NEXSTAR) — Have you ever had one of those annoying calls show up on your cellphone with an unknown number or no caller ID? You are not alone.

According to YouMail’s Robocall Index, the volume of calls nationwide jumped 5.7% in January over the previous month’s numbers. YouMail, a free voicemail and spam blocking app, extrapolates its data from “robocall traffic attempting to get through to YouMail’s millions of active users.” More Here