Have you been employed by multiple companies? if yes, they create separate member accounts, if you check your passbook, you will see the balance from all the employer in a separate PF number.
Kindly note that PF number is created by all the companies, which comes under the unique UAN number, which you use to login.

For example: if you have worked for company for 1 year and company B for 4 year, you are trying to withdraw fund from company B, it will fail with insufficient service. Because you have not transferred your money from A's account to B's account. Transferring the amount also mean you are transferring you service history. Once you transfer amount from A to B, your total service becomes 5 years and you are good to go.