I haven't done anything practical yet, but in our country (South Africa), we've had a law recently that forces the cell network providers to allow consumers to

I haven't done anything practical yet, but in our country (South Africa), we've had a law recently that forces the cell network providers to allow consumers to transfer data around. For basic use (maybe 10 devices), I would be able to share my phone's data plan. I'm on a generous contract that gives me more data than I need (fiber at home). For larger volumes, most providers will either allow you to pool a number of SIM cards' usage into a single account, especially if you restrict them to only connect to a private network. We have this at my workplace on most SIM cards in laptops. There are also companies that supply SIMs to merchants and IoT folk on behalf of network providers. I'd also look into that. In most cases you end up with each SIM having its own data plan. I did some freelance work for one of these companies last year, if you have enough volume, you can negotiate pooling of data.