“Settings” → “Wireless & networks” → “SIM cards” → “Mobile data”: Here do you actually set which SIM card your phone should use for data transfer when not in a Wi-Fi. The other SIM card will not be used.
“Settings” → “Wireless & networks” → “SIM cards” → “Mobile data”: Here do you actually set which SIM card your phone should use for data transfer when not in a Wi-Fi. The other SIM card will not be used.