OP's bug is informal/slangy, and shouldn't be used unless you know the other party very well, but in most other contexts it should be fine to say "Sorry to trouble (or bother) you again". If there really is a need to be more formal, there are potentially two different situations. More @Wikipedia
Get the latest news about Sorry To Bother You. from the top news sites, aggregators and blogs. Also included are videos, photos, and websites related to Sorry To Bother You..
Hover over any link to get a description of the article. Please note that search keywords are sometimes hidden within the full article and don't appear in the description or title.