Twice this week I have been bothered by persistent individuals looking to sell or market something, but in neither occasions has it been possible to simply walk off.
The first took place at my house where a person attempting to sell a product knocked on the door. I politely informed them that I am not interested in their product, they acknowledged my statement but continued to ask questions, to which I had to interrupt and say "I said that I'm not interested" before closing the door.
The second occurred at a coffee shop where I was having a conversation with another person when someone interrupted and began saying "I'm not trying to sell you anything, but...". Given the material they were holding, they were clearly trying to market a graduate recruitment service so I said "Sorry; we're not interested". Again, they ignored my intent and replied "Not interested in having a job?". They would not accept the fact that we are in fact employed and do not wish to be interrupted, and would not leave us alone until I had to resort again to "I told you we are not interested. Please go away.", at which point they acted as if I had been extremely rude to them (of course, telling someone to go away is rude, but I felt out of options) before attempting to insult me ("I'm glad that I'm not your employer") and finally walking away.
In both of these situations, I wished to stop the person from selling or advertising something that I have no interest in, and both individuals had interrupted something else I was doing. However, it was not possible or desirable for myself to walk away as with the answers in this topic, instead, it required the other person to acknowledge my disinterest and remove themselves, however, both were reluctant to do so.
Is there an efficient way of dismissing such people without them attempting to continue marketing their service, and without appearing as rude to other individuals nearby?
For context, these occurred in the United Kingdom, although I expect answers would be similar for other countries.