Deducting an extra installment

<p>Application to add a dependant was sent in April 2017 and was approved in April 2017. At the end of April I was charged for being covered from March 2017. </p> <p> </p> <p>This makes NO sense and is unacceptable!! </p> <p> </p> <p>After phoning customer services, the person told me it will not be rectifeid!! </p> <p> </p> <p>This is theft and I demand a refund!</p>