Who called from +61 406 573 218?

someone with very strong accent saying that there is a transaction made on my account and if I was the one who made it. very suspicious as to how they got my number and knew an amount that I did do a few days earlier. They weren't my bank and I could not make out the business they were calling from even after asking to repeat a few times - very hard to understand their English. May or may not be scam but why call from a mobile number and why not question my bank of maybe suspect transactions. Tried to call number back but does not ring through.