I only know each other's name and mobile phone number. How to sue?

If you can't sue without the identity information of the defendant, you need to hire a lawyer and issue a power of attorney, and then authorize the police station where the defendant's household registration is located to obtain the identity and household registration information of the defendant. In this way, the court can determine whether the case belongs to the jurisdiction of the court and clarify the address where legal documents such as subpoenas are served on the defendant. Lawyers usually need to carry a power of attorney, a lawyer's card, a special investigation letter from a law firm and the defendant's ID number to retrieve the identity and household registration information of the defendant.

The proceedings are as follows:

1, write a complaint. First, write clearly the basic information of both parties of the original defendant, then list the litigation requirements (the purpose and requirements of private prosecution), and finally write clearly the ins and outs of the matter;

2. Bring a copy of the complaint (according to the number of defendants) and evidence (iou or contract) to the local court for filing;

3. After filing the case, go home and wait patiently. The court will serve the defendant with the complaint, the notice of proof, the notice of proof to the public prosecutor and the defendant's reply;

4. A summons will be served after the trial date is determined, and you will go to the court to attend the trial according to the date on the summons.

Legal basis:

People's Republic of China (PRC) Civil Procedure Law

Article 122 A prosecution must meet the following conditions:

(1) The plaintiff is a citizen, legal person and other organization that has a direct interest in the case;

(2) Having a clear defendant;

(3) Having specific requests, facts and reasons;

(4) It falls within the scope of civil litigation accepted by the people's court and is under the jurisdiction of the sued people's court. Article 123 When a lawsuit is brought to a people's court, copies shall be submitted according to the number of defendants.

If it is really difficult to write a complaint, it can be made orally, which will be recorded by the people's court and the other party will be informed. Article 124 A complaint shall contain the following items:

(1) The name, sex, age, nationality, occupation, work unit, domicile and contact information of the plaintiff, the name and domicile of the legal person or other organization, and the name, position and contact information of the legal representative or principal responsible person;

(2) Information such as the name, gender, work unit and domicile of the defendant, and information such as the name and domicile of the legal person or other organization;

(3) the request and the facts and reasons on which it is based;

(4) Evidence and its sources, names and residences of witnesses.

Article 123 A complaint shall be submitted to the people's court, and copies shall be submitted according to the number of defendants.

If it is really difficult to write a complaint, it can be made orally, which will be recorded by the people's court and the other party will be informed.

Article 124 A complaint shall contain the following items:

(1) The name, sex, age, nationality, occupation, work unit, domicile and contact information of the plaintiff, the name and domicile of the legal person or other organization, and the name, position and contact information of the legal representative or principal responsible person;

(2) Information such as the name, gender, work unit and domicile of the defendant, and information such as the name and domicile of the legal person or other organization;

(3) the request and the facts and reasons on which it is based;

(4) Evidence and its sources, names and residences of witnesses.

Second, the prosecution needs to bring the following materials:

1, one indictment, one copy according to the number of defendants;

2, the main evidence materials, and provide copies according to the number of defendants;

3, the identity of the original and the defendant;

4. If another person is entrusted to represent the lawsuit, submit 1 copy of the power of attorney with clear authorization and the ID card of the trustee, and provide the original for inspection.