The context of the following conversation is The landlord sent another bill even though Alex already paid their rent. Alex called their landlord.:
Alex says My landlord sent me a second bill through today..
The friend responds Why did they send a second one?.
Alex responds I don't know, I already paid my rent, so I called them up..
The friend responds What did they say?.
Alex responds They said it was a mistake on their end and not worry about the second payment..