Outgoing calls

Probably the best place to go. Your carrier handles phone calls. They should investigate that. You can also read this. If you can't make or receive calls on your iPhone - Apple Support

This is a user-to-user, volunteer forum. Sometimes it takes longer than three minutes to get a response.

However, as the correct response would have been "contact your carrier", you're doing almost the right thing. Personally, I'd call Verizon customer service rather than going into the store. The people in the store are sales people. They're primary job is to sell you something, not. troubleshoot your account.