Restoring voicemail forwarding settings

[45AMH]

I used my androstore my call id phone to set up forwarding to voicemail for all calls before I went abroad for two weeks.  On my return the phone's call setting shows call forwarding "disabled" and digging through these messages and trying MMI codes I get the "invalid MMI code" response even with WiFi turned off.  How can I restore my call forwarding settings?

[45AMH]

I don't know where the "androstore" came from in that post.  "I used the call settings on my phone" is what I thought I typed

[MI5 · Accepted solution]

@45AMH 

Codes and help in this guide Guide: All you need to know about O2 Voicemail 901 

You may need O2 to disable wifi calling if active on your account.