Hi - I'm not too sure about soya milk lattes to be honest, but I know the Nescafe skinny latte sachets I buy have around 70+ cals per cup and a fair bit of sugar in the ingredients. There is a CS number you can call, which I've taken from their website, I'm sure they'll be able to tell you..0844 8001900.
As far as I can see on the web, 0844 numbers are charged at up to 5p per minute within the UK.