Suspicious caller calling , leaving no message.

they called me twice. 1st time no message.  2nd time saying something about an order and confirming my address.  hung up after I angrily asked "what are you talking about?" It was an accent similar to Indian/pakistani accents.  When I tried calling back the number- a recording says the number is invalid.

called 6x in a 3 hour period no message..i picked up once they hung up

This number has been calling me at least 3 times a day. When I answer no one says anything. I call back and it gives a busy signal.