If you had too little Botox injected, it could be that your muscles were able to recover more quickly. A very small percentage of patients are resistant to Botox. If you had too little, it could have resulted as a result of you not wanting to spend more, or a poor determination by the injector. If you are resistant, there isn't a way for your doctor to determine that until after you've had the treatment. Since there is no real negligence that I can determine from your question, it doesn't sound like you would be entitled to a refund. You should figure out if you got enough. If you did, then Botox may not be a great option for you long term if you're resistant to the treatment and it wears off too quickly. You may want to also inquire if you got genuine Botox or if your doctor is using a different product.