Incomplete income verification by Discovery Key Care Team

In Feb 2019, the key care income verification team requested some documents from me, so that they can put me on the correct income band for 2019. I sent them the requested documents and I heard nothing more from Discovery. In July 19, I noticed that I was incorrectly on the upper income band. They then requested further documents, which I sent them. I am now back on the lower income band.

Discovery: a) where is my refund (the difference between the upper and lower income band, for the last few months), and b) why did you not ask for the other documents in February 2019?