Recently a lot of calls to my mobile have been going straight to VM with no indication on the handset that anyone rang.

This happens often at home, where I have 5 bars of signal due to having a Sure Signal to ensure it because we no longer have a landline.

Texts etc all seem to be fine - it's just voice.

Any idea why? I don't know whether it is more likely to be a network thing or a hardware/iOS thing, but thought I would try here first!

If it was just 1 every now and then I'd ignore it but so far about 6 in 3 days.