Charging me for the month that i have paid for

HI, i would like to thank Hellopeter regarding my query with ADT, they ended up responding to my query although i was not satisfied with the response that they gave me, because i have to pay an amount of money ,which i know that i had paid for that month, when i told them that i have paid for that month, their creditors supervisor didnt respond back to me, when i call him the phone is not working. I will not encourage anyone from my family or friend to have a contract with this Company, it is easy to sign in with them and difficult to cancel with them.