Had my system replaced with new system at the comp...

Had my system replaced with new system at the companys recommendation due to a freon leak in the A coil. The new system worked fine until time to shift from cooling to heating then it had to be reset by turning the breaker off waiting five minutes then turn the breaker back on. Have had them come back several times. Each time the service tech adjusted the freon charge and said some part needed to be replaced. The last visit I was informed this would cost approx $450. I feel that this problem should have been resolved a long time ago.