Sometimes, when a parent wins primary custody of a child after a lengthy child custody dispute, they have very little goodwill left toward the noncustodial parent. This is especially true if the child custody dispute turned acrimonious; custodial parents may begin to feel as though the other parent is acting maliciously, or otherwise doing things that are not in the child's best interest.
The result is that custodial parents may jealously guard their children, preventing communication between the child and his or her noncustodial parent. Some parents tell their children not to return phone calls, or otherwise tell the noncustodial parent to cease contact.
This is an unfortunate situation for all parties involved. Children can begin to feel disconnected from their noncustodial parent, without knowing why. Noncustodial parents may begin to feel they aren't involved in the child's life, which can further damage the family relationships.
Of course, there are legitimate reasons for ceasing contact between parent and child. If the noncustodial parent has a problem with substance abuse, for example, he or she may be a poor influence. Abusive or neglectful parents may also need to be prevented contacting the child. This can be done though a court action in which a family law judge will examine the facts of the case and take the action that is in the best interests of the child.
In cases where there is no abuse, and only hurt feelings and raw emotions, parents should avoid speaking ill of the other parent or attempting to interrupt communication. Keeping a strong relationship with the noncustodial parent can be extremely helpful for children; in most cases, communication should be embraced, not discouraged.
The Huffington Post, "Co-Parenting: Communication With Kids Post-Divorce" Valerie DeLoach, Nov. 20, 2013