Its been 21 days we still didnt recieve our deposit the landlord said he sent it to the mail already?

first we pay are bill on may 3 next day we recieve a 30 days notice without reason.. can they do that they wait for rent payment before they give us a 30 day notice?2nd we move out on may 26 do they supposed give the refund the rest of days that where out..3rd its been 22 days we still didnt recieve our deposit they said they been mailed it already. what we can do?