Is the 4G LTE network extender safe to use for fincial trans actions?

[Ellenj]

It can't be locked.  Which means that 4 unknown neighbors are burning through my broadband allowance.  50 feet is a huge distance in a multi-unit building. 

This is bad enough, but even worse I cannot get a straight answer from Verizon on 2 security questions:

Is my network is still secure? Or can some stranger use a phone to access other devices on my network?

Is it safe to make financial/CC transactions on the extender? I usually turn off Wifi and use cellular to buy stuff from my phone.  Is that still safe, or is it now same as Wifi?

Thanks for your help.