Hearing aids are programmed for your specific needs and the audiologist or hearing aid professional can make changes to them if necessary. If you're not happy with the way they fit or sound when you first get them, be assured that most people require a few adjustments of fine-tuning.
In addition, it takes time for the brain to adapt to hearing sounds it hasn't heard in a while, so your hearing aids may sound more natural after you've had time to wear them. If not, be sure to return to the hearing center with details of what you're experiencing so that your hearing aids can be adjusted to work better for you.
To ensure your satisfaction with hearing aids, most states require a trial period - a specified time period within which you can return hearing aids for a refund. But remember - returned hearing aids can't help you hear better, so give yourself every opportunity to succeed with your instruments by working closely with your professional for follow-up and finetuning in order to ensure your satisfaction.