So I may be best suited to answer this, as I work in fraud for VF.
That SIM plan is a good one, there is no way it came with the cheap tablet. It is on one of the new price plans with inclusive roaming data.
Either the person who owned it forgot, or what is more likely is that it is a fraudulently obtained SIM, that probably came with a good phone.
If you have any questions, just message me.