Question: Who provides fixed line telephone services with numbers starting with 5?
Disambiguated questions and answers: question: Who provides fixed line telephone services with numbers starting with 5 in India?
Who provides fixed line telephone services with numbers starting with 5 in Hong kong?
answer: Mobile TeleSystems India
MTS / HFCL
SMS / Multimedia value-added services, Mobile phone number, and  'Class 2 Service' such as voice over IP
Natural Questions answer: MTS India (from the Wikipedia article "Telephone numbers in India")