In laws and baby names....

With my son we had his name picked out as soon as we found out he was a boy. We fell in love with it and he DID get named it....they refuse to use his name and call him a nickname I honestly hate. I've asked them to call him by his name but they won't. Now I'm pregnant again and after being pushed into telling them the names me and hubby are in love with they tried to change them. We very bluntly said no and immediately were told they would just come up with a new name for the baby when its at their house.... I feel like I'm being disrespected but I don't know how to fully put my foot down on this.