Called me and when I answer they hang up. When you call back you can't get through

I called this phone number and heard a 'not connected' message. Then I answered a call from this number. The person claimed to be from the federal government, with some questions for me about my tax benefits! I said to put it in writing and mail it to me.

called while I was on phone, redialled number only to be cut off. A telemarketer I assume.

calls to my mobile - messages left.
When attempts to return calls - message is 'cannot be connected'

called, hung up on answer. I called back and my call could not be connected