"Impossible to get through on the telephone"

Desperately tried to call regarding a change of appointment letter received this morning for an appointment today! Far to short notice so tried to call to postpone. After 10 mins on phone I had to give up as no answer. I am therefore going to be penalised for not informing as not able to attend. Strongly suggest an answerphone! Very disappointed. . . My letter arrived this morning changing my 12pm appointment today to 3pm unfortunately I cannot make this. I do hope I won't loose any future treatment.