Skeezy billing practices?

I was testing out Keen on a hobby project a couple of years ago and it was pretty neat. Easy to get up and running with nice charts and metrics. Fast-forward a few years, and Keen decides to change their billing to a usage tier based system. I got the mail about it. I checked my usage and I was quite a bit under the 50,000 free events per month, so no sweat. Then I start receiving $150/mo bills from them for my measly 2500 events monthly. Being busy I didn't catch this right away, and now have been charged 3 months at this rate. Once I caught the issue, I wrote to them, expecting to get an easy refund for mistaken charges, but no. They basically pulled a "well in our TOS it says..." on me, claiming that I had been notified by email about the pricing change. I had been notified, but nothing lead me to believe I would start receiving $150/mo bills from them. Now I'm a week into this pain in the ass, and no progress on getting a refund. Is my few hundred dollars really that important to you Keen? Seems like a pretty poor way to build a business if you ask me.