Impossible to cancel a phone line via call centre!

We are trying for months now trying to cancel a phone line on our account, but this seems impossible to do! After going in to the branch twice and trying to phone the call center three times now. No one is responding or doing their work to cancel the line, but they think when they`ve got a signed debit order they can continue to subtract the money from our bank without we getting any service or the cancellation we requested numerously now.<br> <br> Really bad service, don`t know if we`ll ever want to open an account with them again!