ISP reads circuit good (950/950) - I can't read higher than 140. They blame us

Hey guys. I'm going to give a high level overview/rant in hopes for more experienced engineers to help guide this conversation.

We have a branch (~60) using a 1GB fiber circuit. Services have sucked. Many tickets have been opened. It all comes back to "problem is on your side * ticket closed". Issues are slow speeds, intermittent drops, etc.

On the stack (Juniper SRX/EX - very simple) we see maybe 100mbps to various speed tests. I use a gambit of tests in a matrix to get a better feel. We can disconnect the entire stack, hard plug directly into the handoff, 140mbps down.

They plug "their device" in. (Im not the guy on site) and get 950/950. Pack their shit up and leave. They quote "speed tests are inaccurate you're incorrect. So not a SINGLE device regardless of OS (linux,mac,windows,juniper,cisco) cannot get higher than ~100mbps except their device.

Also their device output showed 4ms on their test. Clearly it's not going to the internet. Meanwhile I have another branch in the city, same network stack, same fiber plan and I can blast the entire gig through.

Besides literally taking my hardware from the other known-good site, installing it into the known-bad, what the f*ck can I do to get these guys to do something? There's only one other carrier in the building that we've already started talks with. Idk what else to do. We pay for a gig we get shit. We are -not- under contract anymore.

From the ISP perspective - tell me what you'd like to see from me!