Interestingly enough I've found through my own company that it's not so much whether or not you're solo but rather the price of your software that determines if you can economically offer phone support or not.

I wrote about it here: http://www.followsteph.com/2006/10/10/is-technical-phone-sup...

I then followed it up with an article discussing whether or not companies should charge for support based on my findings in the previous article: http://www.followsteph.com/2010/10/19/should-software-compan...

The short version, under the $1000 price point it's very hard to economically offer free phone support as part of your product. If you're product is subscription based then the same metric applies using the total lifetime value of your customer. Under that price it's very hard to do, whether your a solo developer or a company without charging for support.