I want to brainstorm this. I know about the mute button, but it doesn't work on all pumps. So, how are the pumps getting the ads (getting updated ads)? Are they connected to the internet? Bluetooth? Flash Drive firmware updates?
When we figure this out, the next step is to hack that source.
A quick search for trying to get an ad onto a pump led to this site. Pumps are not all the same, some are uploaded via wired or wireless network. Some via USB. If you want to be a solution, try to be the problem and then work your way backwards.