I would like to know how can I politely tell someone in an email to not call me again, I noticed that I often come across many salesman trying to sell me a services. But I am unsure on how to reject them politely or formally. I would also like to improve my English.
If you really want to be polite, you could send an email like this:
Thank you for your email dated xxxx. I will keep it for reference and will contact you if in future I need your services. Until that time, please do not contact me again.
It would probably be more effective to reply to every email with a single line
This is the email that you would send to cancel your subscription to an automated mailing system: sending it to a person would suggest that you think that they are sending you junk mail.