DairyBelle/C***** InShape fat free plain yoghurt -

I regularly buy the InShape Fat Free plain yoghurt (once a week) because I am a diabetic. When I opened a new 1kg tub on Sunday it tasted sweet and flavoured. I first thought it was my imagination and continued to use the same tub until Wednesday when my son visited me and I asked him to taste. It is definitely not fat free plain. We think it may be full fat, vanilla?? I immediately phoned the Dairy Belle customer line because this could be life threatening for diabetics!!! They passed the buck to C***** who now seem to make the joghurt in the Dairy Belle tub!! C***** told me they had not received any other complaints! Huh??? So that makes my complaint invalid??? They promised to go to that specific batch sample and get back to me, never got back to me. this is not acceptable. I still have the tub if they want to come and taste for themselves, send a diabetic!!!