Legal analysis: 1. If you don't attend the training, you can ask for a full refund. Although the two sides have not signed any written agreement, it can also be used as a basis if the training school has relevant refund commitments in the publicity advertisements. 2. In view of the fact that training institutions and trainees only issue invoices without signing training agreements, first of all, training activities are contracts for providing labor services. If the training result is agreed, it constitutes a contract, while if the training result is not agreed, only the service process is provided, it constitutes an entrustment contract. If no agreement is signed, it is difficult to judge whether to undertake the contract or entrust the contract, it is difficult to understand the rights and obligations of both parties, and it is difficult to judge the breach of contract and responsibility of both parties. But if the invoice is issued, the training is also an entrustment contract. According to the entrustment contract law, the client has the right to terminate the training contract at will, that is, he can request to terminate the training contract at any time. However, if losses are caused to the trustee, it shall compensate for the losses.

Legal basis: Civil Code of People's Republic of China (PRC).

Article 577 Where a party fails to perform its contractual obligations or fails to perform its contractual obligations in conformity with the contract, it shall be liable for breach of contract such as continuing to perform, taking remedial measures or compensating for losses.

Article 584 Where a party fails to perform its contractual obligations or fails to perform its contractual obligations in conformity with the contract, thus causing losses to the other party, the amount of damages shall be equivalent to the losses caused by the breach of the contract, including the losses after the performance of the contract.

However, the benefits obtained shall not exceed the contract concluded by the breaching party.

Predict or should have foreseen the possible losses caused by breach of contract.