One of the worst things you can do when your done with your presentation and ask for the close and the prospect says " I want to think about it" is to try to find out WHY they want to think about it. Don't answer the objection head on. When you do this you instantly break rapport and you start sounding pushy or " like a salesman". The correct technique is to deflect and run a rebuttal sequence that builds more value and trust. Your rebuttal sequence will essentially be a 2nd presentation.
What you need to understand is even if you give the best presentation ever people arent going to say yes right away no matter what. Time needs to pass before they can say yes. Thats why addressing there objections head on doesn't work because there not real there just stalls, when you address them you instantly break rapport and greatly reduce your chances of closing.
This brings me to another HUGE mistake that goes hand in hand with what I went over above. You can't front-load your benefits. Front loading is when you give all your best stuff in your first presentation and then have nothing more valuable to say after they say " i want to think about it". Here's how you do it.. when you give your first pitch always give the weakest benefits, keep it exciting but dry. Your not really trying to get them to say yes after this. You should EXPECT "NO". After they say no you transition into your 2nd presentation where you'll give your next most valuable benefits about your product/service, why they should trust you, and why your company is the best to work with.
Keep doing this over and over again, giving 2nd, 3rd, and even 4th presentations re-establishing those key points, asking for the order after each one, and transitioning through them in a smooth elegant way and you'll close every single prospect thats qualified.
This is how I learned to sell over the phone years ago before the internet even existed, it still works today, and I've made millions of dollars selling over the phone following the exact same process.
(excuse any typos)