The energy companies will NEVER be able to cut your supply except in the circumstances they can already.
They want to sell their energy, not prevent people from using it.
I well remember the power cuts of the 70s. They don't need smart meters to do it! However, one big positive if every property had a smart meter is that those who literally depend on electricity for their life would be assured of a permanent supply should the need for power cuts arise. As it is they would have to go to hospital for the duration.