That's called sales. There are tons of information on the net about this. Search cold call sales, making cold calls on the phone, selling by phone, etc. Most of the time people are busy and not interesting in yet another sales call.
If English is not your first language, it will be much tougher than even this.
The nice thing about a phone call is that you get immediate feedback - you don't have to wonder if they ever saw your email.
One thing you might fix is to stop beating around the bush. End users are busy, so get straight to the point. Opening with "I have a product,,," is like saying "please hang up on me." Wasted words, wasted time.
Try this:
Me: Hello, my name is Bart Simpson, I am a web developer. I currently am brokering the domain name makemoney247.com, and thought you might be interested. End user: Not interested.
See? Now you've made progress. You know they don't want your domain name - time to move on.
Occasionally you'll get a "how much?" Be prepared to answer.