We never recommend using your primary SIM while traveling abroad, as the resulting roaming charges from your primary SIM carrier may be exhorbitant. Since eSIM plans are prepaid plans, you will not only be aware of the total cost of your usage in advance, but you will also be able to avoid any unnecessary roaming charges from your primary SIM carrier. It is also very important to make sure that your primary SIM line is turned off, and your eSIM line turned on while abroad.