Didn't recognise number, they left a voice message but when listened it was just muffled banging in the background no voices at all

I dont know the number so I didn't answer it, it's come up as a scam number with no reply and a possible flubot, scammer, Russian Federation caller something like that. Blocking another number again.

came up as suspected spam so didnt answer, couldnt find anything online so called it back and it said call couldnt be connected. Weird

Calls and leaves silent voice mail