Grandma and Dad are undermining my childcare efforts!?

My 4 month old used to go down so well in her crib she only needed to be drowsy. NOW since Dad holds her on his shoulder to sleep when Im not there she wants to be held to sleep or rocked to sleep or nursed to sleep this is maddening! I had it going so well. Now Grnadma I told her how to warm milk etc and pointed out where a can of formula was in the rare event she'd need it, she definitely wouldnt but just to be 100%sure. I cam home the milk was in the refridgerator and Im like ??? what happened? "Well the milk looked so light I decided to give her the formula instead" O BOY. Ive told both of them please work with me i have a system if u keep it up it works out well for us all. I guess they'd rather make it easy for themself and Im the one stuck with the changes. Im so upset but I cant control what happens when im not around. Any ideas???