Are you looking to promote your business in terms of branding or sales? SMS is part of marketing, but SEO is search engine optimization, which deals with ensuring that your website appears in search results for certain keywords.
For branding you can use SMS (short term) or SEO (long term). The risk of SMS is that you'll have to comply to do not call lists. For SEO you'll have to avail seo consulting services of a reputed firm who can give you results.a wordpress plugin free are available now.