What is the relationship between Skype and Microsoft in the context of the input sentence. Choose an answer from: product/material produced; manufacturer; distributed by; industry; position held; original broadcaster; owned by; founded by; distribution format; headquarters location; stock exchange; currency; parent organization; chief executive officer; director/manager; owner of; operator; member of; employer; chairperson; platform; subsidiary; legal form; publisher; developer; brand; business division; location of formation; creator.

We have a long standing relationship that have evolved their digital transformation from legacy IP PBX to Skype for Business, and now ultimately moving to Microsoft Teams.

Answer: operator