According to Article 53 of the Law of People's Republic of China (PRC) on the Protection of Consumer Rights and Interests, if a business operator provides goods or services in advance, it shall provide them as agreed. If it is not provided in accordance with the agreement, it shall fulfill the agreement or return the advance payment according to the requirements of consumers; And shall bear the interest of the advance payment and the reasonable expenses that the consumer must pay.

In this case, we can see that Mr. Hua chose the personal trainer mode, and the personal trainer clearly designated coach Huang. Personal coaching courses have a strong identity attribute. Unless Mr. Hua agrees personally, Fitness Center A has no right to change personal trainer at will. Now, due to Huang's resignation and Mr. Hua's disapproval of the new fitness instructor, Fitness Center A can't provide the agreed services according to the prepaid agreement, which has met the dissolution conditions stipulated in the Civil Code. According to Article 563 of the Civil Code, "in any of the following circumstances, the parties may terminate the contract: (4) one party delays the performance of the debt or commits other breach of contract, which makes the purpose of the contract impossible;" A fitness center has been unable to achieve the purpose of the contract because of the resignation of coach Huang. Although the contract does not stipulate the circumstances of dissolution, it can be legally dissolved according to the Civil Code.