The amusing thing was that apparently Verizon didn’t setup any sort of billing for my use-case, and since I never used the voice or text the thing just continued to work for a couple of years. It worked after the service cancelled, after the number was reclaimed, and then finally stopped only once the SIM card would no longer register on the network.
Not that I really cared - it was 9600 baud and I only used it a handful of times. Still a funny hack.
But you paid per minute (twice as much for 28k) and it was swiftly killed off by GPRS.
That was never deployed commercially in the US, it tied up too many channels. I was able to use CSD on T-Mobile and AT&T Wireless back in the day.
Worked well enough during unlimited nights and weekends to get on IRC.