FreedomPop, the Niklas Zennstrom-backed mobile broadband company, is adding another $4.3 million to its coffers. The funding will come from its existing investors, but at a higher valuation than its Series A round, CEO Stephen Stokols said in an interview. Since last year, FreedomPop has been selling various add-on sleeves, hotspots and data cards that customers can use to access free and low-cost mobile data plans. More cash will help the company continue to come up with new plans and social features for its service.