In this case, it would depend on your contract with this individual. My personal experience: I’ve only refunded once in 20 years because the client died. I would suggest a consult with an attorney to be sure the contract your clients sign stipulates what if anything is ever refunded so it’s crystal clear to both parties involved.
In addition, I don’t sell packages. It doesn’t help adherence IMO, nor benefits anyone. I charge the same to everyone, except for in home training that requires distance driving. This is the same for 1 session, 10 or whatever. This can also protect both parties and HELP adherence. Even another fitness company I work for bills clients monthly for sessions.
If the client got some ‘deal’ for purchasing more sessions and now is relocating~I’d refund them. The price of doing business but there’s a lot not mentioned in the question.
Hope that helps,