Thank you I have turned off that DHCP thing deleted the device from mobile added it again. Now the other thing you suggested is out of my league to understand that what does it mean port forwarding etc yes one of the leads is attached in wifi router but its for internet providing to cameras.
If its "Out of your league" I can only think the following:-
1) You have never setup port forwarding
2) Somebody else set this up for you and you need to ask them about it
3) You are using some mobile app which either uses p2p (again somebody else set this up) or the app uses UPNP which simply does all the port forwarding for you.
Hard to tell with the limted information so if you could provide more info that may help and also you may want to read up on UPNP / P2P and think about switching it off on your router / camera. Not very secure.
You can google port fowarding, but basically it allows your devices on your internal network to be able to reach the bad internet via a port and the also things on the internet to reach your device on your internal network.