Type *#67# into your phone's numeric keypad, then press your call button. Make a note of the number that’s displayed, including the ‘+’ symbol.
The number displayed is supposed to be the real number of your voicemail box. On Virgin Mobile this number is different from your main mobile number. Since you ported from EE or some other network, perhaps the mailbox number has not correctly updated and calls divert to a mailbox number you no longer have access to.
That was the easy part.
Now ring Virgin Mobile and ask them for the voicemail box number associated with your account. The two numbers should be the same.
If you need to update the voicemail box number then the call centre should be able to do it, or tell you how to do it. If not then type *004*number# and call, where number is the number including the + that Virgin give you.
Have you tried logging in online to your account and enabling voicemail.
I hate voicemail, so have mine switched off, and it does ring for about a minute before you get the message there is no reply or such like depending on which network you call from. All my numbers even home phone I have voicemail off.
However some people do like voicemail, others have voicemail, but never retrieve their messages!
If *#67# reports "not forwarded" then you need to get the number and activate it.
You could try *#61# or *#62#. Both of those should also report the same voice mailbox number.
Or ring 789 and obtain the voice mailbox number. Once you have the number do the *004*number# as per the above post. That will switch on divert to the voice mailbox upon busy or no answer or unreachable.