saved voicemails - how do I delete it?

If you’ve got no new voicemail messages, but have 1 or more saved voicemail messages, option 1 allows you to listen to the saved messages.

If option 1 is not available, sounds like your voicemail is out-of-sync.

One possible solution is turn OFF voicemail in your online iD account.
Leave it OFF for 3-4 days, before turning ON your voicemail.
If that doesn’t fix the issue, I suspect iD Mobile will need investigate further.

Could take a while before this gets fixed - good luck @emmajohnson. 

Hi, it just says I don't have any new voicemails. But ages ago when I finished listening to a voicemail that was left for me I accidentally saved instead of deleting it so I just need it gone

Call voicemail, then listen to your SAVED voicemail, and press 3 while doing this. 
The voicemail system should respond with something like “message deleted”.
Good luck @emmajohnson. 

Yes but what do I press to listen to my saved voicemails?

When you call voicemail, if there aren’t any NEW messages the system offers some options, one of which is to listen to your saved messages.

Good luck @emmajohnson. 

Hi, none of the options available allow you to even access your saved voicemails. But I know I have at least one from when I listen to a new voicemail it always says I've got one.

Hi @emmajohnson 

Please let us know how you get on with the above suggestions from @andewhite.

Tom