To name and shame a big company that has just screwed me over

[SmallBuisnessOwner]

Name change.

I did some work for a huge company, it was exactly as they requested (even against my advice that I thought they were missing the point). It was over a weeks work.

Was delivered to them they said thanks bla bla and I invoiced.

Now a month later I'm expecting payment and they are saying they were expecting more from me due to the track record of achievements I told them about at the begining of negotiations. But these achievements are averaged out across all of my work, I can't guarantee anything for a single peice.

They are asking for another one for free.

Aibu to refuse to do so, request payment ASAP and if not (on my social media) make a post where I talk honestly about what happened to me and by whom?

I would ask them exactly what it is they feel you have under delivered on and point out you previously mentioned XYZ concerns at the start. Say what you could do in the future but that would be chargeable. Ask them to pay within 7 days.

I've had a response that it will be paid this week a day after filing the small claims court. Thanks so much to the helpful people here