That means they CAN switch. Otherwise they would do without. Their need for the service is stronger than their need to do business with the source. To convert these people you must be able to determine exactly what they think they are getting from the other source so that you can convince them that you can do a better job. Using the principles of advertising to create a precise message that reaches only that person and that stresses only that benefit.
Every successful advertiser has to have a unique advantage.
Without it, the advertiser cannot establish their brand as being different. In this type of advertising, the message is short and focuses on the advantage. This is probably the easiest type of advertising. If the unique advantage is doubtful, you must abandon it and find a creative way to use what exists. If you are not better than an alternative, stress the fact that you are eager or easy to use.