Your router at the radio site have to get a public addressable IP address from your ISP (Verizon) and it must be open for incoming traffic. Private IP addresses on the WAN side like 10.x.x.x, 192.168.x.x or 172.x.x.x can not be accessed from the internet. Contact your ISP and request a public IP address open for incoming traffic. Here in OZ I have found the hard way that only the company '3' deliveres public addressable IP address on 3 or 4 G mobile broadband.
This has nothing to do with static=fixed IP addresses or dynamical IP addresses. If you get a public dynamical IP address you use DDNS to find the actual public IP address of the radio site.
In theory your ISP can give you a private IP adr and do a 1:1 NAT to a public IP adr so whenever the public IP adr is addressed from the internet all traffic goes (=is NAT'ted) to the private IP address, but I do not think any ISP will use their firewalls in that way for millions of customers.
73, Palle, OZ1RH.