The infotainment system gets pretty well neutered without a data plan, at least in the 2022. You will be limited to AM/FM/XM if you subscribe to it. The apps (including google maps) will cease to work or update. They have changed the names of the packages 2 or 3 times since I got my rig in feb of 2022.
Net, though, you will need have at least “OnStar Connect” to get your remote commands and maps and apps to work. If the classic OnStar stolen vehicle, crash assist, hit a button for an advisor is a service you want, that is Safety and Security. If you need Video Streaming, Games, and the WebBrowser (if equipped) you need is Connect Plus. I thought you also need Connect Plus for the HotSpot, but it may depend on the model year of your vehicle. It’s all broken down at OnStar.com.
I’ve had some success getting a discount by calling them and asking to “cancel my service.” As the first word out of my mouth. But that works best after you are a paying customer.
Best advice, let it expire, see what is missing, call and get that turned on for a month, then call to “cancel my service” to begin negotiating. Same schema works well with SirriusXM if you value their service.
Good luck.