Hi,
One thing I have learned is that all children are different, even within the same family. What works with one doesn't work with another.
It is good your son is not getting his own way, despite his 'back chat'. Try not to get into an argument with him.... (my eldest is an expert at dragging me into an argument and as soon as I allw myself to get dragged into an argument, she's won!!!!))....You could try saying 'You can say what you want, it's not going to change what is happening' or 'It's not ok to speak to me like that. Don't speak to me like that'. Make sure you model good behaviour too...
If the way he is speaking to you doesn't get a major reaction from you, and when he speaks nicely he is praised I'm sure he'll grow out of this phase.