How to stop Staffies from Barking/Welcoming people

Hi

we have a very busy household with people in and out all day... Maddy, Harvey and Chloe are super friendly but shew can they make a noise when people come into the house... which is sometimes cute but when they do it to some people they see 3 or 4 times in a day it can become very annoying..... Harvey does not stop his high pitch bark until you give him a tummy rub, Maddy and Chloe almost sing to you.... not sure of what kind of command to give to make it known that they can stop now... gratefull for any suggestions xxxx