Upgrade calls no longer going to voicemail

[Lancsla]

I upgraded from a BlackBerry to Android last week.

I upgraded the contract with the help of an advisor. 

Everything went through ok however since then although I access voicemail regularly, calls are no longer going to voicemail. 

I've tried ringing customer service but the system keeps telling me there's a long queue then disconnects me.

I've checked handset settings and Googled the issue cannot find any problem.

When I dial 901 I can access the voicemail menu as usual, reset greeting, listen to old messages.

Incoming calls are just ringing out, not going to voicemail.

[MI5 · Accepted solution]

@Lancsla 

Check your diverts are set correctly for unanswered Guide: All you need to know about O2 Voicemail 901