Naspers Ltd. , Africa’s biggest company by market value, is seeking partnerships with mobile-phone operators on the continent to boost its video-on-demand business and help compete with U.S. giant The owner of Africa’s biggest pay-TV provider is planning to build on a joint venture agreed to last year with Kenya’s largest company, Safaricom Ltd. , to roll out online service Showmax at more affordable data prices. Safaricom is 40 percent owned by Newbury, England-based Vodafone Group Plc.