From the owner profile access System>Users, then click on any secondary user you have and turn off calls and SMS, this only works for secondary user profiles, now, it is not recommended to disable these apps as some things wont work but in theory you could install some other dialer and SMS app and set them as the default dialer and SMS, then disable the preinstalled ones, after that you could uninstall the apps you just installed and you won't have default SMS and dialer apps available (you can enable them again later).