Landsdowne are ******!!

I received an email from Landsdowne for my complex saying my levies would increase by 7% and that they would now bill separately for Domestic Effluent. When I received my statement, my levy has now increased by 15% and when I call to query the amount she still claims it is 7%. Their accounts department is useless and they can clearly not do maths if they cannot see my bill has increased by 15%!