How prevent my phone from hiding the country code? My Samsung s8+ called id only shows the local phone number without country code. (023455678 instead of +123455678)

How can I fix it?
source Go through this link for more understanding.

Conclusion:


A leading 0 or "(0)" is a way of showing that you have provided the full phone number in the national format.  The 0 represents the national dialing prefix; the caller will know to omit the leading 0 if they are placing a local call.
A leading + is a way of showing that you have provided the full phone number in international E.164 format.  The "+" will tell the caller that they need to dial the international dialing prefix such as "00" or "011" if they are calling from outside the country; and that conversely they may need to dial a "0" or "1" if calling from within the country.