The answer is yes, because good SEO is built into the website.
If you buy a car you generally expect it to come with an engine. It's built into the car and you don't buy as an add on extra after you've taken delivery. As a result I don't offer SEO services as an add on to a website we weren't involved in at the outset.
What many 'SEO' companies will do is manage external stuff such as Social media, online magazines, blogs and such. This is all good stuff, if done well and there are many genuine experts in this. There are also a lot of individuals who seem to think this is a neat way to empty your pockets. We can certainly recommend the former types who will do an excellent job for you. Sadly the 'SEO' business seem to be a popular business with with rogues. So do ask and we'll point you in the right direction.