Fencing erected but slanted

[jkz]

In February 09 l had close board fencing erected at the time when paying contractor's l asked was it fitted correctly; as it appeared to be varying and inconsistent, l was told it was all the correct height. Since then the
Fencing is gapping l have brought it to there attention and have been told they will correct. But l now see that the base of timber there are gaps appearing whereby the ground is not parallel what can l do about this.