Hi MaryEllen,
If you have several responses to an account, I would suggest that you portray the account based on the NPS distribution. In your example, the score would be -30 (7 passives and 3 detractors). That gives a much more insightful perspecitve of the account and that there are some stakeholders that needs attention. If you used average 6.8, it would be tempting to label the account as a "passive" (probably also beign the reason for your question).
If you consider the NPS as an account management tool, you would be providing great insight to the account manager that there are 3 detractors in the customers organisation. They may be influencers, if not decision makers - and having no promoters that leaves some relationship work to be done.
Hope this is useful.