2013 Ford Focus 2.0TDCI Battery

My wife's car is 2 years old.Bought brand new from Allen Joss. 2 weeks ago I noticed strange behavior from the gauges on start-up. At the car wash on Sunday 14 Feb the car wouldn't start.I jumped the car and drove home.I removed the battery filler caps inspected the water level.The battery was bone dry.The car was last serviced by Allen Joss September 2015.There is no spillage or residue from boiling or evaporation.The service manager Danie at Allen Joss just says sorry they will not replace the battery under warranty and ensured me the battery is number 2 on their service checklist.BS.If that battery was filled to the correct level at the last service the battery would not have packed up.I was a service manager at Mc Carthy and no ways was that battery topped up at the last service.New battery according to Ford R2100