Call each and first ask if they know what tinnitus is. If they do ask if they believe they can be of service to you. Some will and others will not. If they say yes, ask what kind of therapy they believe will help you and why. As in all forms of therapy, you must make the final decision of who to work with.
Fees are generally quite reasonable and hypnotherapists tend to be pleasant and caring individuals.
If the self hypnosis tapes, for some reason fail to reduce your negative emotional impact of tinnitus or the volume of the noise, you may return the program for a refund.