According to the documentation, the conference call feature should work on Lumia 520.
However, while Add Call feature works and I call the other person, the Merge Calls button seems to do nothing - clicking it should merge both calls but does nothing.
The same feature works like a charm on the other Lumia I have access to, the 925. Both work with the same mobile operator.
Is this an issue with this particular model (520?), this particular phone or it just doesn't work on 520 even though the docs says it should work?