I've seen this place mentioned in other threads and my MIL recently switched and all it took was a phone call:

https://www.masspowerchoice.com/worcester

Reading through the site I don't really see a downside unless Nat Grid drops below the posted rates (in which case you seem to be easily able to switch back.)

The one thing I haven't seen yet is if all the other delivery fees will change, but from a kw/h view it should meet your criteria.