O2 keeps telling me I have a voicemail, but when I try to listen to it, I get redirected to top-up

[Sesmar]

I have a Voicemail notification that I can't delete, just saying "New voicemail, O2". The problem is that when I try to listen to it, I immediately get redirected to the top-up service. It's basically an automated machine telling me that my balance is 0, that I need to top up, and giving me a bunch of options on how to do it.

I actually went and topped up now (I only rarely use my UK number), and I should have data etc... But I still can't listen to this voicemail, and I still keep getting redirected to the top-up service. Frankly, it's a bit annoying that I can't delete this notification or listen to it. And it would be nice if O2 actually let me listen to my voicemails. What should I do here?

[MI5 · Accepted solution]

@Sesmar 

If you are trying to access voicemail from abroad you need credit as bundle allowances won't allow a call to VM from abroad.

If you have a voicemail pin set up you could call your VM from a landline Guide: All you need to know about O2 Voicemail 901