Cant change Voicemail number

[Anonymous]

Hi, and thanks for reading this.

I got a Tesco locked Sony Xperia Miro for Christmas. I wanted to keep my O2 account so I paid £20 to Tesco for an unlock code. This worked fine. All except the Voicemail. Its still set at 905. Each time I change it I get a "VM number change unsuccessful" message. Having googled the problem I came across ##5005*86*901# to change it to o2. But then I get an "invalid MMI code" message. Has anyone know of a definitive fix for this?

Thanks in advance.

[MI5]

MMI codes usually start "*#" not "##"

[Anonymous]

I don't really know this issue - but try **5005*86*901# ?

It seems more likely that it would begin with * and not # (just a guess).

[Anonymous]

I got the MMI codes here http://community.giffgaff.com/t5/Learn-giffgaff-Top-Tips/iPhone-codes/td-p/48140

I did try your suggestion *5005*86*901# but that too gave me an invalid MMI code message

[MI5]

*# (asterix first)

[Anonymous]

No, *#5005*86*901# still gives the 'Connection problem or Invalid MMI code' message