Being ignored while trying to close an account. No assistance, shocking service

I have been trying for over 4 months to updating my banking details for my standard bank online share trading in order to liquidate the account. The company seems to completely ignore the fact that the banking details they have on file do not exist anymore. I want to close the account, I have tried several times sent several emails regarding the need to close this account. Nobody has bothered to reply. I have sent the new banking details, proof of address and explained what needs to happen. However, even after 4 months the banking details are not updated. Honestly, I don't understand why trying to update details is so hard in this day and age, or is it they don't want me to close the account? Either way this is really disgusting service. I have literally emailed regarding trying to get advice and no reply either. If I knew this would be the experience I would receive, I would have used another share trading account.