User A: We need to do some check on our data. So you need to add in a new function for this, we can't use your system otherwise.
Me: Ok then.
Spends 2 days or so to get it working
Me: So this is the function we'll add. Can you confirm that its ok?
User A: Ohh...but now I'm not too sure about this. Let me confirm with my team lead on this.
User A: I just checked. Good news,we don't really need that function now. I think we can use it with the current one anyway haha. And I just confirmed this so no worries.
So I just wasted my time then. Great.