Reported WAN IP does not match assigned WAN IP

I’m using a Peplink Balance 200 with two IP providers. One (Viasat) is working fine. The other (local MiFi provider) is the issue. The router says the WAN IP is which seems odd. Sure enough, when I run whatismyip I get a very different WAN address, one that makes more sense. This has screwed up my DDNS setup for that specific MiFi provider. In all other aspects things are running fine.

I suspect the problem is with the MiFi provider rather than the Balance. However, I’d like to prepare myself for what will be a frustrating disucssion with the MiFi operation’s (limited) technical support staff.

Has anyone encounted this type of situation before?

OK. I did some searching. Looks like my ISP must be using Carrier Grade NAT here. Big problem for me. I’ll have to talk to them about it.