I'm not a native or teacher:
But I would like to suggest the following sentences:
-If we have any further doubts, we will come back to you.
-We have been informing/have informed you that the water consumption is increasing. However, you have not taken any step to rectify the situation/no step has been taken to rectify the situation.
-We tried to contact you, but you were not available.
Student or Learner