I get a lot of "link exchange" requests. I doubt this will prevent them, but it gives me a convenient place to put a recent response I gave to one which I can use as a template later to saver time. Generally I find out a little about both the SEO company, and the company that purchased the SEO services. I then email both the SEO scammer and the company who purchased their services.
In other words, if you are going to request a link exchange, please note that I generally contact your customer directly and tell them how lousy link exchanges really are, and that they are wasting their money on you.
Dear SEO Scammer,
Please add this email address and my website to your DO NOT CONTACT list. I am not interested in participating in so called "link exchanges" for SEO purposes.
Dear website owner,
I'm sorry to hear you've wasted your money on this SEO scammer.
You should perform a virus and malicious software check on any of your systems that may have visited [SEO Scammer's Website] as Google reports that several of their pages attempt to attack website visitors:
If you purchased search engine optimization services from a different company, then it appears they are outsourcing it to others ("SEO Scammer" above sent his message from India) - which is fine, but it means you paid extra for another layer of middlemen who don't actually do the work themselves, meaning they may not even know how best to represent your company on the internet.
While SEO scams generally bring some results for a short period of time, the best method to increase your sales, page rank, and listing in searches is to provide great content in the form of articles, FAQs, etc. Even if you only post one new page of useful information every other week you'll soon see a permanent increase in website visitors researching voltage conversion products, and more importantly those that do come to your website will immediately see that you have the expertise to sell them what they need. Posting new content on a regular basis raises your profile in search engines as "recent" content is valued more highly than older content. Further, using a variety of messages and phrasing will get those people that use unusual search terms to find products such as yours.
Good luck with your business.