Login keep disconnecting when tethered

I'm using a couple of Smarty SIMs one in my phone and one in a Huawai WiFi hotspot.

When I connect to the internet from my computer tethered to either it works absolutely fine for general browsing, but really poorly for certain logged in services (eg website CPanel, GMail, Banking) because the session cookies expire very quickly. CPanel and banking are completely unusable as they barely stay logged in for more than one page refresh. Gmail stays logged in longer but even that is disconnecting several time a day.

I'm guessing that it is to do with IP address being refreshed frequently. I've tried changing the WPA to the highest security version but don't see any other options under Hotspot which I can change.

Is there a way around this as it makes Smarty an extremely poor choice for MiFi boxes?