I agree with anav. If those devices are not yours, you should not be tinkering with them.
Having said that…
LTE devices are typically used with CGNAT-setup. Meaning, there is no way you can access them remotely unless they first get out themselves to a device having a fixed IP (can also be dynamic dns but that complicates things a bit more). And then you can go back through the tunnel created first by the LTE device.
Your requirements however are not very clear (and I am frankly hugely disappointed anav did not bring it up 
).
If you are not going to address any of the connectivity aspects, what do you need access to those devices for then ? To do what ?
Or is the true requirement something else behind those LTE’s you need to access /control ?
The whole story on the table, please 