An estimated 4.1 billion robocalls were made nationwide in June, according to data compiled by YouMail, an app that plays out an out-of-service message from your phone. Since February this year, the number of calls made to phone users across the U.S. has risen more than 40 percent, YouMail says. About 29 percent of the calls made in May were scams, with the rest being telemarketing, payment reminders or debt collection reminders. The safest thing to do when an unknown number pings your phone is to let it roll to voicemail.”]