Cannot connect to voicemail Samsung GT E1200i

[MPS]

When I hold the voicemail key, I am being connected to my own number with a message saying the person you're calling is unobtainable. How can I change this to connect properly to voicemail?

Thanks very much.

[Cleoriff]

@MPS 

Check out this guide Guide: All you need to know about O2 Voicemail 901 

[MI5 · Accepted solution]

@MPS 

Try Settings >Applications >Call >Voicemail

or Settings >Phone >Voicemail and set the voicemail number to 901.

Press Save before closing the menu.

[MI5]

However, according to this help from Tesco mobile, it cannot be edited.

If the phone is unlocked from another network to use on O2 you'll just have to dial 901 manually to listen to voicemail.

[MPS]

Setting voicemail number to 901 seems to have worked.

Thanks very much.

[MI5]

You're welcome