Calling Restriction

I have a friend with a Verizon cellphone. For the past week, when I try to call him, I get the following message: "Welcome to Verizon Wireless. We're sorry, the number you have dialed has calling restrictions that prevented the completion of your call." Conversely, when he tries to call me, when I answer, I get the same recording (he hears my phone ring)??? We can text without a problem. FYI, I just called him and the call went through. As an aside, he has never blocked my calls or forwarded his phone. Thoughts???