Your opening line isn't as important as the closing line. After giving them a price you need to keep them talking, otherwise 9 times out of ten they'll just ask you for a leaflet as they would prefer to be in control (it's human nature). You need to take that control away from them, as you want to control when you are going to do them.
I start my pitch by saying we are in the area such and such a day, that way you have set them up for the close. After giving them a price and telling them the regularity you can generally tell by body language and the way they talk whether they are keen. If they are then say something to the effect that 'we are in the street such and such a day, we can clean them and leave an invoice to pay online if you are out, will that be okay?'
If they don't seem keen usually there is something on their mind, this is where the hard work is, trying to tease out them the problem (always remember that if they initially asked you the price they are interested!). Usually the problem is back access issues, or they have a dog, it could be anything ... even the rabbit in the garden. You need to keep them talking, find out the issue and don't just give them a leaflet as I can guarantee by this time they have asked for one ... once they have your leaflet they are back in control and you've made it difficult for yourself. Many people don't like to say no, usually it's a case of 'just give me a leaflet and i'll call you back' (they will not call you back).
Canvassing is a complex game to get it spot on, but even not getting everyone spot on by following a few simple rules you can get success ... the best tip I can say is stay in control of the close and don't walk away when they ask for you for a leaflet.
Also don't have anything in hands as they will try and read it. Need to make as much eye contact as possible, so my canvasser tells me lol 
That's a top tip, sounds like a half decent canvasser
