And that would just give you _one_ person who can only do one call at a time. If you can't justify hiring an employee to do this, you aren't a target customer of this service anyway, I imagine.
Most businesses aren't in SF, most startups aren't even in SF. Yes, I know you think you guys are the center of the world. But there is a reason call centers are in lower income areas and its not because people are just getting around to decentralized support centers.
Amazon has been doing this for.. nearly a decade already? Other companies do this in the Philippines. It has nothing to do with justifying an employee, it has everything to with justifying hiring 3-4 employees (or even 10) rather than one service who is just going to be a glorified answering service.
Think of it as an AWS analogue. If you are a company running some large predictable number of servers with a constant load, it's probably cheapest to just have a rack of servers, if the scale can cover the people to maintain them. If you have varying loads across different days and seasons though, AWS might make a lot of sense since you don't have to pay for servers sitting around idle. That flexibility comes at a premium.
To take it a step further, if you're a slightly smaller company that values time and agility and doesn't have a large dev ops team in-house, you might want to use a PaaS, like Heroku.
I'm just saying that the obvious immediate market for this to me seems to be towards b&m or medium-touch product sales businesses that are _in_ areas like SF. Many Bay Area startups are selling services to other Bay Area startups, that's just the reality of this sort of thing.
If you're not their target market, you're not their target market. If you are looking to hire people and this ends up being a viable alternative you will save a ton of money.
I worked in/around call centers for most of my first career, I know the score.
That's my point, its not a viable alternative ESPECIALLY if you are going to hire people.