A new social media campaign is putting fashion retailer Next under intense scrutiny, with activists alleging that the company told 1,416 unionized garment workers at a Sri Lankan factory they were out of a job through WhatsApp. The accusations, shared in a widely viewed Instagram reel, are fueling renewed criticism of fast fashion's human and environmental costs. What happened? In a recent post, creator and campaigner Venetia La Manna said in he…