The network code "03" can refer to different mobile network identifiers depending on the context:

• In Germany, "03" is part of the Mobilfunknetzkennzahl (mobile network code) for Telefónica (formerly E-Plus), which operates GSM, UMTS, LTE, and 5G networks

• The number "3" or "Three" is also a major international mobile network brand owned by Hutchison 3G Enterprises, operating mobile networks in multiple countries including the UK, Ireland, Austria, Denmark, Sweden, Italy, Hong Kong, Macau, and Indonesia. The brand was founded on 3 March 2003 and provides 3G, 4G, and 5G services

• In the Philippines, the mobile network code "03" is associated with SMART, one of the major telecom operators there

Therefore, "03" as a network identifier can relate to Telefónica in Germany, the "Three" mobile network brand internationally, or SMART in the Philippines, depending on the country and context. The "Three" network is particularly notable as a global brand with extensive 3G, 4G, and 5G coverage in several countries