If your dog becomes severely knotted or matted, it may well be beyond the level that can be reasonably recovered. Should the discomfort during attempts to remove the mats prove to be more than the dog could humanely be asked to endure, then your dog will be clipped short. The hair will be cut underneath the level of the mat, leaving the hair as long as it is possible to do.
The alternative to clipping the dog, is to leave it in a matted, neglected state, which we are not prepared to do so, and we will not torture your dog trying to remove them.