office mgr

The Takhar group has been calling our office and leaving messages on our voice mail for several months now. Today I happened to answer the phone when they called. They are all prerecorded messages demanding that their call be returned. There is no opportunity to speak to a live person. After the message plays they simply disconnect. However, they never indicate who specifically they are calling or what it is about. Our office has just been ignoring the calls. They can keep wasting their time as no one here knows who it is they want to speak to. Any other suggestions?