How to turn off messaging service

[#1]

Is there a way to switch off the messaging service on a line which has broadband but no phone service. A local rather senior lady has been waiting since the 11th December for openreach to repair the line and due to local travel restrictions at weekends they are not expected to arrive for a few days at least.
It would be better if we could get a fault notification on the line in the meantime but don't expect that would be possible.

[#2]

I meant for Voicemail to be switched off

[#3]

It can be removed from the line using the Remove call features page in the Home Phone control panel. However I'm not sure how long it takes for that to take effect.
It can be activated again using the Add call features tab.

[#4]

I may have it wrong but I believe that I can only do that from the phone that isn't working.
I tried to do it online but failed to see how it could be done.

[#5]

Just click on the link that spraxyt  provided and log on the the account you want to change - then select the feature you no longer wish to have. It does not have to be done from the line you want it removing from, but you do need to log on as the account holder, if that is not you.