MR 6500 Pro from AT&T - No port Forwarding, IP Passthrough, UPnp or DMZ

I've got a Netgear M6 Pro 6500 from AT&T to control a security camera (Firmware version NTGX65_12.01.16.01 - Up to date). The camera has a WebUI easily accessed with a browser from within the private network. The problem is that I can't get to control the camera from the public network. I can view the camera feed in my phone using the P2P app provided by the camera manufacturer. The issue is that I need to access the camera WebUI remotely to program the camera functions just like when I'm accessing it within the private network. 

The MR6 gets a public address that changes every time I restart the router. (Once I know the WAN IP I should be able to connect to the camera server. If the thing works I may get a static address)

I have experience with these cameras working on internet-wired networks. I set up port forwarding and everything works ok. This is the first time I'm using a mobile router. The 6500 ignores Port forwarding, IP Passthrough, UPnP, and even DMZ. It seems that I have a brick and AT&T support can't figure it out either.

Somewhere I read that the firmware installed in the ATT version is not the same as the one shipped from Netgear.

Any suggestions about how can I make this work?

Thank you