Is there a scam going around? VM calls.

Ok, past the obvious jokes about VM and scamming, im getting a lot of calls from a VM call centre and they say they cant hear me. 

Always to my mobile, and they ask for the account holder by name. It’s not me but it is my wife’s account, although i tend to do the talking. It is my number which is registered on the account. 

I guess ive had 15+ over the past few weeks. I can hear them clearly enough but they never hear me and hang up. Our contract is due for renewal soon so i imagine this could be legit, but no way will i call back on that number.

Just wondering if this is legit.