Cell c bad service

ID ********** 154089 Account # ********** 39 i sent a request on the 15th April to cancel my fiber line. I got an email back saying some will call me. no one called. come may i received a may bill. only yesterday the 6 may when i called in did i get an email saying that they tried to call me but could not get hold of me. no one called. i want this cancellation to be back dated and for a new bill sent which should only be up until the 15th of may