It is critical to understand the economics - and perhaps more importantly, potential economics - behind these calls, their frequency, and why it is a different person or company calling you almost every time. In order to understand, you have to see it first and foremost from the perspective of the companies that are calling you.
First, consider how many local businesses there are in world. If that's too much, just consider how many local businesses there are in the United States. To help put that in perspective, simply consider how many local businesses there are in your own city or town. Depending on where you live, the answer is hundreds of local businesses in the smaller town, thousands and thousands in the larger city. To give an example, at one point in the city of Las Vegas alone there were 15,000 Realtors. The answer, there are hundreds of millions of local businesses out there.
So let's just take the Realtors as an example. If I can contract just 1% of those in Las Vegas (120) or even half a percent (60) to, say, $300-500.00 a month or more for online marketing services I'm collecting $18,000 - 60,000.00 a month from that tiny fraction of Realtors alone! (And why wouldn't they all want it!) But it gets better because this is the internet. I'm not bound to any one local city. I can contract Realtors in Los Angeles, San Francisco, New York City, Houston, Miami, Chicago and every small ho-dunk town in between. Now I'm making $180,000-600,000 a month just off Realtors. But it doesn't stop there. What about roofers and painters and handymen and plumbers, electricians, restaurants . . . In short, there exists out there a vast sea of virtually endless businesses! I don't even need to dominate the market to make gobs and gobs of seriously big, easy money. A tiny fraction can make me rich!!!
Rule#1 - You're a number in a vast sea of local businesses.

Rule# 2. You're a number in a vast sea of local businesses . . . and they want your money.
Rule # 3. Sales reps don't do SEO.
Behind the sales rep is the company sales manager constantly reminding them of two things. One, all the gobs and gobs of money they will make if they sign people up for contracts from the vast sea of businesses and two, all the gobs and gobs of money they wont be making if they don't sign people up for contracts out of the vast sea because they will be out of a job.
Rule # 4. But sales reps do need to sell SEO or they'll go penniless and hungry.

Behind or along with all of the money and sales perspective, however, is of course the product of value: your local SEO. It is critical for you to understand that this is secondary to pretty much any company out there who calls you on the phone. This applies even to large reputable companies with widely recognized names. In fact, these big name corporations may even be worse.

A client of mine was paying Intuit 99.00 a month for a specific type of SEO service. Intuit would submit a blog article every month linked to the clients website. He had been paying them for almost two years which means Intuit should have submitted 24 articles on his behalf. A search for links to his website yielded the result of two. (If there were more that couldn't be found by Google or Yahoo they were of no SEO value anyway.) So in short this business owner paid Intuit almost 2,400.00 for two blog articles. Intuit was collecting money and screwing him. It doesn't stop there with Intuit. but we'll leave it at that for now.
CitySearch is another big name reputable company. They claim they will list you in their network of 2,000 websites. I have never seen them actually live up to this claim (and once if they do and those site can't be found by Google or have maybe even been banned, its still a rip off). CitySearch also engages in another common scheme that sounds good but really isn't. Like many companies, they offer to set you up with a specific new phone number so you can actually track how many calls you've gotten from their service. Once you understand that your real business phone number is the essential strain of DNA Google uses to track you and rank your listing, you'll realize that as good as it sounds, using a different phone number actually takes all of your organic potential away. Further, it creates a mess of duplicate listings for your business all over the internet. Any ranking power you may have already achieved is now compromised and might possible be detrimental. You tell me. Would it be better to have Google find 200 citations for your one business phone number, or find 100 for one phone number and 100 for another? Further, beyond the phone number other critical information can become confused in the internet directory ecosystem. This means that Google will not be able to make consistent sense of your business information and the result will be lower ranking and possible penalization for spam. Getting rid of these listings once they are up is also near impossible (and keep this in mind: even when you cancel). So as good as it all might sound, a "tracking" phone number is nothing but very poor SEO and that's certainly not something you should be paying for.
The big companies are also experts at making it near impossible for you to cancel once you have started. The Granddaddy of continued horror stories in this regard is actually the most recognizable company of them all – YellowPages. (Just ask the client who actually faced bankruptcy trying to pay off his YellowPages contract . . . )

If these companies do employ human beings to do their SEO work it is usually in one of two scenarios. First scenario, we employ a larger number of lower paid entry levels employees to do the dirty work. This means the minimum wage "tech intern" who isn't paid enough to really care about your business and do an effective job. The second scenario (far less likely), we employ a small number of really good SEO techs and pay them decently. This small number of really good SEO techs, however, can easily become overwhelmed with too much, endless work as we sign up every Realtor, roofer, plumber and handyman in the country to our services. Bottom line, your paying to be put into a clogged conveyor belt where you will wait for months and months for anything to get done and in the long run it will never really get done for your business effectively.
So what’s the conclusion of all this? SEO is a very personal business. What's going to work for you in your regional market and field is not necessarily what is going to work for someone else in their field and their particular regional market. You can't sign up and pay for cookie-cutter SEO. You need a qualified human being who can and will analyze all the details of your unique situation, figure out your best strategy and then actually implement it. After implementing they need to stay on top of it, making sure it is working, looking for areas that might be improved and working to eliminate any potential problems. They also need to be someone you can talk to when you need them, have an issue, have a problem, or even have a new idea. (This actually happens all the time.) You’re the business owner and SEO can really help you, but only if you’ve got someone genuinely working on your side. This wont happen if you're just another number in a vast sea. Then again, there is a very minuscule chance that it just might. If the person on the other end of the phone is interested in making a living by actually helping your business succeed, you could be on to something. As a client of mine once told me "Now I always have to give these calls some amount of consideration, you doomed me . . . .because that's how I found you."