Well for Me and being in a 24/7 Relationship, Disagreements will and are going to happen. The key to your question was the Respect.
I provide many ways to communicate, The Journal, The Bitch box and a well worded respectful statement on your position.
I have found disagreements that are not aired will lead to resentment and resentment leads to acting out... a Place no one wishes to go
If My slave disagrees with a order and that order is within the negotiated limits of Our contract I expect it to be done. She then has her methods of recourse as mentioned above.
I find it works best for Me through the years if the slave/sub always has a way to express his/her self to her Master
J D