How to handle Wifi interference from other companies in shared office building?

Hi all. So ive hit a bit of wall with this issue we have been having at our office which I could really use some guidance on. Our office is surrounded on most sides by another training provider who seems to think that any and every room they move into needs around 2/3 AP's. We are having issues where their AP's seem to do a channel scan every 30 minutes or so and change their channels around which causes all our AP's to hit 100% interference and connections drop off (We are using Unifi AP's and Controller). On a normal day 2.4Ghz is 100% taken over with their 4 SSID's overlapping themselves and the 5Ghz band is around 80% used up. We have tried to speak to them however they have said that it isn't their problem and suggested we just boost the signal of ours (we tried that for the sake of it but it just ended in more interference) or move all our devices over to 5Ghz which we currently have set to do if the device supports it. We have plenty of AP signal strength to cover the office for both 2.4 and 5Ghz.

We've wired everyone we can in but the top dogs at the company come in and demand that their teams calls must not drop for even a second while on wifi. Have any of you guys had this kind of issue and how was it resolved/dealt with as me telling and showing them the graphs and stats seem to fall on deaf ears. To add to all this we have also had the students and staff from the other company complain to us because every 30 minutes they all lose connection (which when i suggested they might want to check that setting they ignored).