Frustrated client

I have been a long standing client of them and nobody in their accounts can assist me with my query I tried several times to cancel my month to month contract with them they keep billing me and then they say they have no record of me ever speaking to anybody meanwhile I have all the call log details it is extremely frustrating to get somebody in a, senior position to talk to nobody ever calls back and you have to explain the same thing over and over this has now resulted in me canceling with them