Was anything past volume 7 ever released in English?
As @Krazer mentioned above, Satisfaction Guaranteed was one of the projects that Tokyopop was publishing. However, in 2011, the company was shut down, and the publishing of the project went along with it.

Wikipedia cites volume 7 as being the last (English) release as of July 31, 2010. According to AnimeNewsNetwork, there is a theoretical volume 8 in English; however, that information was posted prior to the suggested release date of the volume, and it appears to have never come to fruition.

So it does seem that volume 7 is the last official English version. You'll probably have better luck looking for a Chinese or Japanese version (even English fan translations past volume 3 appear to be scarce*).

* Unfortunately, we cannot link to scanlations or online readers for legal reasons.