Ever get an on-site pump out of your gray/black tanks?

Last weekend we stayed at the expo center in Topeka for 4 days. Only have a 25 gal black tank, and by the 4th day it was full. Would have been nice to have this kind of service. We only had a shore power hookup, nothing else. It's also a bit frustrating in that when we camp like this, we use paper plates and don't utilize the sink very much. Since we have separate grey tanks - showers are very limited.