On our most recent trip to Sri Lanka, we actually ended up just working with our 3 UK sim playing cards (thanks, ‘Go Roam’ protection!), but throughout our 1st vacation in 2016, we purchased local sim cards and topped up with information as we wanted. Guinea-Bissau Sri Lanka precise information: http://collinoesgs.howeweb.com/2698243/the-smart-trick-of-tour-sri-lanka-that-no-one-is-discussing