I've noticed that some changes have been made to voicemail.
Normally if I have a temporary greeting active, and I phone voicemail, the first thing I hear is "your temporary greeting is active. To revert to your standard greeting, key 3" instead of you have X new messages. I had a temporary greeting active yesterday and I called voicemail to turn it off, but I didn't hear "your temporary greeting is active. To revert to your standard greeting, key 3"
Why did you make these changes O2?
If it's not broken, don't fix it!
I'm not affiliated with O2
The great team in your local O2 store will be able to help you further, if you need it