Citibank Sunnyvale Branch Phone Number

Calling from Outside the USA: If you are calling a phone number in the USA from another country, you need to start with the country code "+1". This is the international dialing code for the USA.

Calling within the USA: If you are calling a phone number within the USA from another number within the USA, you don't need to include the "+1" country code. Just dial the 10-digit local number.

In summary: Use "+1" when dialing internationally (from outside the USA), and skip it when dialing domestically (within the USA).