[HELP] GSM Providers

I purchased a vehicle monitoring software and now I need to connect the devices to the main software server. I’ve never used a GSM, I don’t know what it is and I don’t know how to connect it.
can I buy a simple SIM card and activate a subscription? (so will I have to buy 50 SIM cards with 50 subscriptions?) Or are there other providers? I’m sorry but I want to understand.

any of you if you can help me send me a PM or can reply on this thread.