Cox Communications is throwing in the towel on efforts to market mobile phone service to its pay TV customers, telling subscribers that it will discontinue the year-old service on March 30.

Among the reasons Cox cited for canning its mobile phone efforts were increased competition from 4G networks and its inability to access "iconic wireless devices," a reference to Apple's iPhone, which is only available to AT&T and Verizon mobile phone customers.

Cox's exit from the mobile phone business won't allow it to market a quadruple play of pay TV, Internet and mobile and landline phone to customers. Verizon gives its FiOS TV and Internet customers a $10 discount on mobile phone service, which helps boost subscriber retention.

But it's too early to predict how Cox and other cable MSOs may attempt to enter the mobile phone space again. Cablevision is currently testing how it could use its extensive WiFi network to deliver phone service--a tactic that late Apple CEO Steve Jobs was also reportedly considering for his company.