Selling a used car, a certain platform says they have a "Guaranteed Sale Service": first, drive the car over, they appraise it at 100k yuan, help you sell it, and if it doesn't sell within 15 days, the platform will buy it at 100k yuan.

I feel like there's a safety net, so I feel at ease.
I sign the contract and leave the car.
After 10 days, I ask if it has been sold. Customer service says they are promoting it, just wait a bit longer.
On the 14th day, customer service calls: "Brother, a buyer is offering 92,000 yuan, is that okay?"
I say: "No, it's not okay, we agreed on a guaranteed minimum of 100k yuan."