Closure of rcs account

hi i payed up my rcs in full but after trying to close the account and numerous occasion phoning them ,when they put me through to the closures department nobody ever answers the phone because they dont want to close my account and now after 1month they say i owe 150 for what???i asked to close my account when my balance was nil please sort this out im tired of this ****py service from rcs very annoying,i will not pay another 150 for nothing plz close my account