GM says that they'll do an OTA update of the Bolt's telematics, based on your VIN. I checked and the advisement was "press your OnStar button" They don't mention whether or not there's a charge for folks like me who don't have an OnStar subscription, but my Bolt is a 2020, bought new in November of 2020 and has about 23,000 miles on it.
Is there a charge?
As an aside, I find it more than a bit stupid on GM's part to not have had 4G capability from the start; the phase-out of 3G was planned many years ago.
What say you?