Impossible to cancel ADSL

I have just been retrenched from my job and decided that it would be better to cancel some of my accounts to avoid running up bills that I can't pay. One of the accounts is my MWEB 2MBPS Uncapped ADSL data (month to month) account. I phoned their call centre and was told to log in to my account and under 'My products' tab there would be a place where I could cancel my services. I logged in and found that there was no 'My products' tab. Called the call centre back and was told that a technician would call me back, which they did, two days later, and told me that they did not know what the problem was and that someone would call me back again. Well it's now 4 days later and no body has phoned me back and they are trying to take the next months debit order from my account that has no money in even though I tried to cancel this account 3 days before the end of last month. So it seems that once you have Mweb ADSL YOU CAN NEVER CANCEL IT AGAIN!! The more I ask then to do it manually the more they say they can't.... If they can't then who can???