Limiting data from HA for low cost LTE plan

Hello everyone, hope this is the right area for this topic.
I am running a lite version of HA (from imager/other specific os/home assistant).
RPi3 is connected to a sensbender gateway(usb) and alcatel LTE router.
I am using Mysensors integration only and a few sensors. (no camera or data hungry devices). Until now every thing runs perfectly.
I was hoping to run it remotely with a 500MB/month card, but running this one day only reached 200MB ! How can we limit data from the RPi and HA. Anyone with had this experience and found a solution ? Please help.