Bad Service - Cancellation charges inacceptable

Called Call Centre and obtained email address to cancel. The email address and reference number provided were incorrect.<br> Emailed originally on the 27/01/2016 and cancellation from month 01/02/2016 (email proof available)<br> Also no service provided after housebreak and other service providers assisted instead even after panic button were used but were not working.<br> Still charged another month after cancellation. New Invoice delivered to my house on the 11/04/2016<br> This is unacceptable.