The agencies keep getting shut down. They do re-open, but one needs very recent local intel.
Agree with the tip of Hong Kong. If you really only have time in GZ, suggest a massage parlor, ideally with a Chinese colleague. Event the glossy one that look like posh hotels will at least give HE. Sometimes they have a better floor. One I used to go to, my Chinese friend told her 4th floor. On my own, I was only taken to 2nd or 3rd for massage rooms (showers, pool and lockers were on 1). 4th floor was FS. But normally not for non-Chinese.