Does a smart meter send energy readings anyway?

What triggers a smart meter to send a reading?

If you lower your frequency of sending gas and electric readings in the web app will the energy company update your meter with that information so it sends the information less frequently or does the meter just continue to send the data but the energy company ignores the half hourly data?

If it's the latter, there seems to be an element of trust that the data isn't being used anyway?