Based in Mobile, Ala., Callis serves customers in key business markets across the Southeast.
Officials for Ridgeland, Miss.-based C Spire announced the acquisition in a new release Wednesday.
C Spire officials say once the acquisition gets regulatory approval from the Federal Communications Commission, the merger will help it expand its markets and offer comprehensive business solutions for customers.
C Spire expects final regulatory approval of the merger within the next 60 days.
Callis started in 1999 as a paging provider. It became a facilities-based competitive local exchange carrier and Internet service provider in 2005 and in 2009 became a cloud-based unified communications company.