[Q] Some knowledge on data usage and roms topic

So, recently I just flashed Cyanogenmod onto a Nexus 5 and all is well, however I got a text from my mobile service provider, called Vaya (an Australian company) saying I had used approximately 135gb this month. I know 100% for sure I have not used this much through my data. Although this text came just after I had finished rooting and flashing the phone. Could the flashing have caused my phone to use a ton of data? I don't see how it could of but if someone can explain that'd be awesome :)