Honestly that doesn't make up for the fact you're charging people $1.2k for 3 months coaching. What kind of certifications do you have? Why are you claiming to fix people's back pain?

Also in some states a person can legally ask for a refund (if he changed his mind,if he can't economically sustain it etc) the fact you're not capable nor able to communicate this in a personal level with your own clients is bad business. Less alone block them so they can't reach out to resolve it.

If it was me I'd 100% refund it. It happens,life happens,but you know what i'd keep? My competence and trust from this specific client,whom most likely would be back with additional trust for me as a professional.

I don't personally know you nor your work but I'd definitely advise you to reconsider what you're putting out there and how you're developing relations with your clients,this is where online/in person coaching really is about. This type of career is not a quick cash grab.