Shared hosting environments are probably not worth it but that decision is of course up to you. If you want to dedicate the time and resources then by all means.
I can't give recommendations on a specific agency but most I've dealt with don't do much more than send some letters anyways, unless you're willing to spend a decent amount.
Also, keep in mind without the customers social security number it's much much harder to report this to the credit bureau's. Legally, interstate there's probably nothing you can do with amounts that small, but you would have to check with the laws of your state with "theft of service".