Let me describe the scenario first so you can get the nuance better. I was looking for a new apartment from several agents. An agent "A" to which I will refer for the following explanation provided me with services such as searching for several apartments that conforms to my budget, bringing me to look at the apartments, etc. It was on Friday. As no apartments satisfied me, the staff will provide me with other options in the next Monday.
As I have no time to wait, I go to other agents and I found an apartment on Saturday. Sunday afternoon, there was a call from the agent A saying, when you will come tomorrow? My reply is as follows:
大変申し訳ありません。新しいアパートを見つけてしまいましたので・・・
And his respond is
オッケーです
Question
How polite is おっけーです when it is said by the shop staff to a customer?
Is there any feel of disappointment in this context?