DD is nearly 10 and over the last few weeks has become incresingly cheeky and backchats a lot.
If i tell her to stop doing something she does it one more time,has an answer for everything,sometimes refuses to do what i ask her to do eg. brush her hair amd even worse she sometimes speaks to me in a contemptuous manner often with a raised voice 
Im hardly a novice,i have 3 grown up sons and am fairly strict.We have a lovely relationship otherwise and she is a nice child its just this.
I need a plan of action and thought here would be a good startting point.
She has a phone but hardly bothers with it,doesnt watch much tv or have regular pocket money so im struggling with sanctions/rewards.