I need advice about what to do

What would you do if your SO 5 year old was disrespectful? I've told his father and he's told his son to listen and respect . I feel he does but he's being told not to give me respect. because his mom tells him that and I've asked him has mommy and told you im mean,bad or not to listen? He was afraid to answer but if I ask did daddy say that - he says mommy. So he gets it.......however He's too young to understand. and of course she will deny it. Its tough