Company doesn’t want to cancel cellphone contract

I had two cellphone contracts with Intellicel and I finished one of them and I cancelled the contract on time . I called few months back to check if indeed the contract is cancelled and I was told that it is cancelled but now I find that the very same contract still appears on my credit report and am told that the account in question is in areas as I didn’t cancel the contract while I did. And again intellicel doesn’t update their information with credit bereaus it last updated In january and this is affecting my credit score . I called Intellicel this week and I spoke to abongile and daynel who promised to investigate the matter by listening to recordings but still they did not get back to me