watson-conversation - ワトソンの会話の文脈

Question

現在、ワトソン チャットボット会話アプリケーションを使用しています。ユーザー入力に応じて特定の段階で、コンテキストを更新する必要がある状況に遭遇しましたが、これを達成できませんでした。

I tried setting the context = {}, if the user input isn't in the Array, but it seems to check the context at every stage of the Application. 

if(context.city !== array[i]['city']){
        context = {};
 }

what i am asking the user is to input a list of cities, which is in an Array. If the user inputs a location that isn't in the Array first, it let's the user know that it isn't in the Array. If the user inputs a city that is not in the Array after inputing a city that is already in the array, it is returning the last context. 

for example,

City = Boston.
You just input Boston, price is 20.
Then if i do City = Atlanta(Bearing in mind Atlanta is not in the Array)
it does city is Atlanta, price is 20. 

Any idea how to fix this, on any steps i can follow to stop this from happening?