I am an Entrepreneur experienced in e-commerce and business development. I am happy to share my experiences and my perspective.
I recommend adding live chat to your e-commerce site, some companies offer ticket system with the live chat feature (LiveChat is one example). And when you are unable to chat you can turn the live chat feature off and the system will allow the customer to send you a message instead (to your email email).
In terms of phone, we use line2, great service as you can use your computer to call and get a toll free number. You can also forward the number to your cell or home phone, OS app or Android app, etc...
Nothing better than trying few options and see what works for you. The ones I mentioned above are very cost effective (less than $40 per months) and you can change to different solutions if not satisfied without impacting your customers.
SEO is very time consuming that is why good SEO companies charge a lot per month. If you are willing to save money and put time into SEO you have two options:
1- Do it Yourself - A lot of material available online
2- Get SEO consulting services - These are individuals or companies that will analyze your site and keywords and provide you with a detailed report on what is missing to rank better but the bulk of the work is done by you.
I recommend number 2 and I might be biased because I offer SEO consulting services but that is an affordable and faster way to get on the right track.