Hi Sandy,
Your domain name represents your business. If they are different it can make past clients have a harder time finding you again and create confusions as people often look at domain names as business names. A false but popular habit.
.net verses .com also has draw backs as people automatically type .com (then they get the wrong business) so I'd be interested to know if the .com is also a VA services? If so you are then driving business to them.
If my business name were not available in a .com I'd either go with myname.com or something completely unique and put a powered by, sponsored by, in partnership with... type comment in clear but not distracting view. Then make sure that the unique/myname.com is stated on your business cards and welcome materials as well.
You are also hurting your rankings as your domain name won't be repeated anywhere on the site, but your business name will be. Domain names are a big help in
SEO, often more so then most people realize. Which means searches for your business will pull a domain up that doesn't match and that 'other' company with your .com domain name, which means you may loose business that way too.
I think the best suggestion I can give would be to do a business-name.com as the dash will NOT hurt rankings, in fact it helps google see the word seperation! Don't use underscores though as underscores hurt google rankings (but don't effect yahoo). For example my business domain of campaignpromotions.com has been bought by someone for resale so I use campaign-promotions.com instead.
P.S. Your domain name is your online business card. It is more important then your paper business card as you work virtually.