What if the person traveling wants to use a SIM card from his country of origin in order to receive important calls but don't want to incur incredible expensive

What if the person traveling wants to use a SIM card from his country of origin in order to receive important calls but don't want to incur incredible expensive data roaming costs and decides to use a local prepaid sim on the iPad to achieve that? Just... stop arriving to those definitive conclusions when there are a couple of variables involved.