have to disable 4g to ensure 'm using wifi

I would like to use wifi whenever possible when at home.  If there is a connection through wifi, does this connection take precedence over the 3G/4G link? Or do I have to turn off the 3G/4G link to ensure i'm using wifi instead of my data plan?  If i have to turn off the 3G/4G capability, does this affect calls or texting?

Thanks in advance!